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A free scan shows the junk files, broken settings and background clutter dragging Windows down - then fixes them in one click.Free scan · Windows 10 & 11Crashes, No Sound, or Screen Glitches?
Random freezes, missing sound and display glitches usually trace back to one bad driver. Find and replace yours safely.Free scan · under a minuteIf an external drive is missing after upgrading to macOS Tahoe 26, do not erase it first. A disk can be powered but blocked by accessory approval, hidden by Finder, merely unmounted, encrypted, formatted in a Mac-incompatible way, or physically failing. Check whether macOS sees the device, its partition/container, or only fails to mount the volume, then work through these eight fixes in order.
First check your exact Tahoe build at Apple menu → System Settings → General → Software Update. Tahoe is macOS 26, but behavior can differ between 26.x releases. Reports of HFS+, exFAT, and Time Machine mounting problems are anecdotal and do not establish a universal Tahoe bug.
Quick triage: what does your Mac actually see?
- Nothing in Disk Utility or System Information: Start with power, cable, port, hub, enclosure, and approval checks.
- Visible in System Information but not Disk Utility: The USB or Thunderbolt connection is detected, but storage enumeration may be failing.
- Visible in Disk Utility as a physical disk without a volume: Suspect a partition-table, enclosure, or filesystem problem.
- Visible with a greyed-out volume: It may be unmounted, encrypted, corrupted, unsupported, or blocked by filesystem software.
- Visible in Finder but inaccessible or read-only: Check format, permissions, encryption, free space, and third-party drivers.
Use Disk Utility → View → Show All Devices to reveal the hierarchy of physical disk, container, and volume.
1. Connect the drive directly and restore power
Remove the dock, monitor, hub, or adapter temporarily and connect the drive directly to a Mac port. Try another port and a known-good data cable; USB-C describes the connector, not the protocol or speed. A charging cable may not carry the required data signal.
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- Connect desktop HDDs and multi-drive enclosures to their AC adapter.
- Give a powered hub or dock its own power supply.
- Disconnect other high-power USB devices while testing.
- For a portable bus-powered HDD, bypass an underpowered hub.
Apple recommends reconnecting the device, trying another port, bypassing hubs, and checking hub power when USB devices are disabled or underpowered: Apple’s USB troubleshooting guidance. No LED, spin, or System Information entry after these tests points toward the cable, enclosure, power supply, or drive hardware.
2. Approve the USB or Thunderbolt accessory in Tahoe
On Apple-silicon Mac laptops, Tahoe can supply power to an unknown accessory while withholding data access if it was denied.
- Unlock the Mac and disconnect and reconnect the drive.
- Choose Allow when the accessory prompt appears.
- If no prompt appears, open Apple menu → System Settings → Privacy & Security.
- Scroll to Accessories and review Allow accessories to connect.
- Choose Automatically When Unlocked or Always Allow only if that fits your security policy.
Apple explains this control and its data-access effect at Allow USB and other accessories to connect to your Mac. It mainly affects new or unknown accessories on Apple-silicon laptops, not every storage failure; managed Macs may enforce the setting.
3. Make external disks visible in Finder
This fixes presentation only, and applies when the volume is already mounted.
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- Open Finder and choose Finder → Settings.
- In General, enable External disks under “Show these items on the desktop.”
- In Sidebar, enable External disks under “Locations.”
If Disk Utility cannot mount the volume, Finder preferences are not the underlying repair.
4. Mount the volume manually in Disk Utility
- Open Finder → Applications → Utilities → Disk Utility.
- Choose View → Show All Devices.
- Select the greyed-out volume beneath the external physical disk.
- Click Mount.
A successful mount activates the volume and places it under Finder’s Locations; the button changes to Eject or becomes unavailable. If Mount fails immediately, record the exact error rather than repeatedly clicking it. Apple’s procedure is documented at Mount a volume that’s been ejected using Disk Utility.
5. Run First Aid from the volume upward
First Aid checks and may repair filesystem structures; it cannot repair failed heads, SSD cells, a USB bridge, or a bad cable.
- In Disk Utility, choose View → Show All Devices.
- Select the lowest-level volume and choose First Aid → Run.
- Run First Aid on the container above it.
- Finally run it on the physical device, if available.
Apple specifies this volume-to-container-to-device order and recommends macOS Recovery when normal macOS cannot repair the device: How to repair a Mac storage device with Disk Utility. If the disk clicks, freezes Finder, disconnects, runs extremely slowly, or reports I/O errors, stop repeated scans and protect the data before further repair.
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6. Inspect and mount it with Terminal
Use Terminal for identification and diagnostics, not blind command copying.
diskutil list
diskutil info /dev/diskN
diskutil mount /dev/diskNsM
diskutil mountDisk /dev/diskN
diskutil apfs list
diskutil unmountDisk /dev/diskNReplace diskN and diskNsM with identifiers shown by diskutil list; never type those placeholders literally. Recheck the identifier after reconnecting because it can change. If the disk is absent from diskutil list, mounting commands cannot solve a physical or USB-enumeration failure.
Never use eraseDisk, eraseVolume, partitionDisk, or similar destructive commands unless the contents are backed up or intentionally being discarded. Avoid random fsck or force-mount commands as a first response, especially with encrypted, APFS, RAID, or failing disks.
7. Check format, encryption, and filesystem software
In Disk Utility or Finder’s Get Info, identify the format and whether the volume is locked.
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| Format | Typical macOS behavior |
|---|---|
| APFS | Native modern Mac format; common for current Mac storage and many Time Machine disks. |
| Mac OS Extended (HFS+) | Older Mac format; legacy volumes may expose compatibility or corruption issues. |
| exFAT | Common Mac/Windows exchange format; corruption can prevent mounting. |
| MS-DOS (FAT32) | Broad compatibility with file-size and volume limitations. |
| NTFS | macOS may read it but does not provide normal native write support. |
Apple’s format guidance is at If your Mac can’t save files to an external drive. Also check for a password-protected encrypted volume, a Windows BitLocker volume, RAID or proprietary enclosure, or a disk previously used by Linux, NAS hardware, a camera, or a console. Outdated third-party filesystem drivers can interfere after an OS upgrade; verify Tahoe compatibility before installing or updating one. A mounted read-only volume is different from an unmounted one and may reflect NTFS limits, corruption, permissions, or hardware deterioration.
8. Test another Mac and choose recovery, replacement, or reformatting
- Try another Mac with a direct connection and a different cable.
- If the drive is removable, test another compatible enclosure or SATA-to-USB adapter.
- If it mounts elsewhere, copy critical files immediately before investigating Tahoe, drivers, or ports.
- If it fails on multiple computers and cables, suspect the enclosure, bridge board, power supply, or storage media.
Do not initialize a disk that appears blank or uninitialized if it previously contained data. A second computer can isolate compatibility or connection problems but does not prove intermittent hardware is healthy.
What the result means
| What you see | Likely category | Next action |
|---|---|---|
| No LED, spin, or Disk Utility entry | Power, cable, enclosure, or hardware | Direct connection; change power, cable, port, or adapter. |
| Accessory charges but no data appears | Approval or bad data path | Unlock and approve it; change port and cable. |
| System Information sees it, Disk Utility does not | USB bridge or storage enumeration | Remove hub; try another enclosure or Mac. |
| Disk Utility shows a greyed volume | Unmounted, corrupt, encrypted, or unsupported | Mount, inspect format, then run First Aid. |
| First Aid succeeds but Finder cannot open it | Visibility, permissions, driver, or deeper issue | Check Finder settings, Get Info, drivers, and another Mac. |
| First Aid repeatedly fails | Filesystem damage or failing hardware | Protect data; avoid erasing; consider recovery. |
| Works on another Mac | Tahoe, permission, driver, port, or cable issue | Copy data first, then compare software and connections. |
| Clicks, freezes, vanishes, or is extremely slow | Likely hardware degradation | Stop repeated scans and seek professional recovery. |
| NTFS mounts but cannot be written | Native macOS NTFS limitation | Use a compatible driver or reformat after backup. |
| Previously populated disk appears uninitialized | Partition-table or filesystem damage | Do not initialize; use a recovery workflow. |
Special cases to handle carefully
Time Machine disks
Time Machine storage may contain APFS containers, volumes, and snapshots rather than one simple volume. Do not erase it until another complete backup is confirmed.
RAID and multi-disk enclosures
A RAID volume can fail to mount while individual disks remain visible. Do not repair or reformat individual members unless the enclosure or RAID vendor explicitly instructs you.
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Encrypted volumes
If an encrypted volume is visible, authenticate and unlock it. Do not erase or repair it blindly.
Recovery Mode
On Apple silicon, shut down, hold the power button until startup options appear, choose Options, and open Disk Utility. On Intel Macs, restart while holding Command-R. Startup screens can vary by model and security configuration.
When to stop troubleshooting
- The drive clicks, repeatedly spins up, disconnects, or freezes the Mac.
- Disk Utility reports repeated input/output errors.
- Data is irreplaceable and the device is unstable.
- The drive is detected only intermittently or becomes dramatically slower during scans.
In these cases, minimize power-on time and consider a professional recovery service. Recovery software is appropriate only when the device is detected and stable. Tools such as Disk Drill, R-Studio, and EaseUS Data Recovery Wizard for Mac are not guarantees and cannot substitute for imaging or laboratory work on failing hardware. For severe mechanical, RAID, or irreplaceable-data cases, services such as DriveSavers or Ontrack provide evaluation-based recovery.
Reformat only after the data is safe
Erasing initializes and reformats the device, destroying its existing volume structure and contents. Apple documents the process at Initialize an external storage device in Disk Utility.
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Proceed only when the drive is empty, the data is backed up elsewhere, or recovery is no longer required.
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