SSPI Handshake failed I am facing a strange situation... On a SQL2016 on Windows 2019, I have an application running on windows2019 that connect to the SQL server using a domain service account (same domain as the 
SQL Server).

In the SQL server Log, I can see those errors:

Login failed. The login is from an untrusted domain and cannot be used with Integrated authentication. [CLIENT: x.x.x.x]
SSPI handshake failed with error code 0x8009030c, state 14 while establishing a connection with integrated security; the connection has been closed. Reason: AcceptSecurityContext failed. The operating system error code indicates the cause of failure. The logon attempt failed   [CLIENT: x.x.x.x]


Well, the first error does not make sense as the login is in the same domain.

The weird thing is that when they reboot the app server, then suddently, those error goes away and are replaced by "login succeeded". And then, hours or days later, it start failling again.

If it was the spn, it would never work. If it was a TLS issue, I'm guessing it would never work as well.

What could it be that make it work for a certain time and then fail ?

Thank you.
maybe your account is being locked out... are you using it someplace else? Did you check in your DC for events for this account? You could use a SQL Server login instead of a domain account.