[validate_tgt] (0x0020): [RID#988] TGT failed verification using key for

[Ken Hornstein]

>(0x0020): [RID#988] 2359: [-1765328339][Service key not available]

This means, "I tried to validate the TGT using a locally stored host
key, I was able to get a service ticket for 'host/local-host-name', but
I couldn't find that service key in the local keytab (/etc/krb5.keytab,
typically)'.

Looking at the code, that could be caused by one of:

- You didn't actually store the key for that principal in your local keytab
- A permission problem with the local keytab
- Confusion about the local hostname and what is stored in the local keytab

If I had to guess I'd suspect the first one; that involves coordination
with your AD admins.

--Ken