In the Performance Center UI, a "Failed to connect to PC Service" error message is received when trying to run a scenario (which is not even reaching the initializing state). The Lab Management's "System Health Check" didn't show any problems. Environment was working the day before.
In the PC Server's LTLogger logs, we found the following error: "ERROR HP.PC.DAL.Impl.DbContextImpl - OpenConnection. System.Data.SqlClient.SqlException (0x80131904): Login failed. The login is from an untrusted domain and cannot be used with Windows authentication."