After upgrade from 8.1 to 8.5 release, Task Server fails to register. In this situation, Task Server had an account 'xxxx' which was a local account on both the SMP and Site Server.
Error code: HTTP status 401: The request requires user authentication (0x8FA10191)
Error note: Authentication failed, server refused to authenticate with provided credentials
Error note: Authentication failed, server refused to authenticate with the provided credentials or the user account is locked
Account used did not have correct permissions.
If step 2 is successful, there may be an issue with the Agent Connectivity Credential as specified. If the Account is on a Domain, the Domain must be referenced. i.e. Domain\UserName