500121
Moderate
Microsoft · Windows
Microsoft sign-in blocked due to unmet authentication requirements (commonly MFA/conditional access).
Quick Answer
Error code 500121 on your Microsoft Windows means: Microsoft sign-in blocked due to unmet authentication requirements (commonly MFA/conditional access).. This is usually fixable — see the step-by-step guide below.
Affected Models
Applies to all models
Likely Causes
How to Fix It
1
Reattempt sign-in and complete MFA challenge.
2
Use approved authentication method configured by admin.
3
Ensure device compliance status is healthy.
4
Review sign-in logs for exact policy trigger.
5
Admin may need to update policy targeting/exclusions.
Pro Tip
This fix requires some technical knowledge. If you're unsure about any step, consider contacting support or a qualified technician.
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