If Windows logs a SCEP enrollment error with Event ID 87, HTTP 429 Too Many Requests and HRESULT 0x801901ad, the enrollment service is reporting that it received too many requests. That entry alone does not show that your TPM is broken or identify why the request was rate-limited. Read the full event before changing anything; the endpoint and response details determine what the error means.
What “Code 87” means in this event
In this context, 87 is the CertEnroll Event Viewer ID, not enough information to identify the underlying failure by itself. The HTTP status and HRESULT are separate values: a Microsoft Q&A report dated July 15, 2026 describes an enrollment request to a Microsoft AIK endpoint at microsoftaik.azure.net that received HTTP 429 and HRESULT 0x801901ad. The report also includes Retry-After: 20, the interval stated by the server in that particular response. It should not be assumed to apply to other events. Read the reported event details on Microsoft Q&A.
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HTTP 429 is a rate-limit response: the service is telling that request to slow down or retry later. It describes the response received for that enrollment attempt, but does not establish what triggered it, whether the cause is on the PC or service side, or whether a Windows update is responsible.
Check the full event before troubleshooting
In Event Viewer, open the event and inspect its General message and details. Record the endpoint, HTTP status, HRESULT, response text and any Retry-After value. Event ID 87 alone is not enough to choose a remedy.
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- HTTP 429 and 0x801901ad: the request received a Too Many Requests response.
- A retry interval: use only the value shown in your event; the reported value of 20 belongs to one response, not a universal schedule.
- HTTP 400 or a different response message: treat it as a different error rather than applying 429-specific guidance.
Does HTTP 429 mean the TPM is faulty?
No. In the July 15, 2026 Microsoft Q&A report, the user described the TPM as ready while also reporting the 429 response. That does not prove every device is healthy, but it shows that this event can appear alongside a ready TPM. The event alone is not evidence that you should clear the TPM or replace it.
What to do about repeated entries
If this is a personal PC
First confirm that subsequent entries contain the same endpoint and response. If they do, note when they occur and whether the event includes a retry interval. The available reports do not establish a universal fix, a confirmed cause, or a reliable time after which the entries will stop. Avoid changing enrollment or scheduled-task settings based only on the event ID.
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If this is a work- or school-managed PC
Send the administrator the complete event message, including the endpoint, HTTP status, HRESULT and any retry information. Enrollment may be managed by organizational policy, so the administrator is the right person to check the device’s enrollment configuration. The cited reports do not establish that changing a scheduled task is generally safe or recommended.
Do not confuse HTTP 429 with a different Event ID 87 error
A separate Microsoft Q&A report dated July 26, 2026 describes Event ID 87 with HTTP 400 and a message that V2 AIK requests using P-256 ECC keys are unsupported. That is a different response from HTTP 429 and needs separate diagnosis; advice about rate limiting does not explain an unsupported-key message. See the separate HTTP 400 report on Microsoft Q&A.
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What is and is not established
Microsoft Q&A and ElevenForum discussions include users reporting that repeated events later stopped, but those accounts do not establish why they stopped or confirm an official remedy. They also do not prove that a particular Windows update caused the 429 pattern, show how widespread it is, or confirm the current status of the enrollment service. Treat claims about a specific cause or guaranteed fix as unverified unless supported by information specific to your device or an official notice.
The main 429 report and user discussion are available in the Microsoft Q&A thread and the ElevenForum discussion. Forum experiences are individual reports, not confirmation of Microsoft policy or a universal resolution.
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