← cd ~/errors
// entra id sign-in error · accounts, passwords and sessions
AADSTS80001
OnPremiseStoreIsNotAvailable
What Microsoft says
The Authentication Agent is unable to connect to Active Directory. Make sure that agent servers are members of the same AD forest as the users whose passwords need to be validated and they are able to connect to Active Directory.
How to fix it
Microsoft doesn't publish a specific fix for this code beyond the description above. This site groups it under accounts, passwords and sessions, based on that description, so start with the steps below.
How to investigate
- Confirm which account the user actually signed in with. A personal account or the wrong tenant causes many of these.
- Check the user object: enabled, licensed, in the right tenant, and with no recent password change or reset.
- Look at the sign-in logs over a few days for a pattern, such as repeated failures from one IP address.
- Search the sign-in logs for the request ID or correlation ID from the troubleshooting details on the error page.
Tools that help
The description is quoted from Microsoft's error code reference. The grouping and investigation steps are this site's guidance.