The target principal name is incorrect. Cannot generate SSPI context.

I'm getting an error when trying to connect to my database server.

I'm using SQL server reporting services, and my DB admin created a report to test the connection.

Starting today, my SQL server reporting services are not working.

I get this error message:

The report server couldn't connect to the data source using the information you entered. Make sure you've entered the connection string and any credentials correctly.

I have tried this form different work stations, still get the same error.

I double checked my company firewall and it's not blocking the traffic.

I ran a wireshark on the db1 server, the client initiating the transaction and I see from the wireshark that the domain controller it connects to first is not allowing the connection.

The specific error is: KRB error: KRB5KDC_ERR_C_PRINCIPAL_UNKNOWN

I looked this up online, but can't find much.

Every stream I looked at in wireshark shows me the same thing.  So something on my DC is not allowing this traffic.