Error message may display:
Msg 233, Level 20, State 0, Line 0
A transport-level error has occurred when sending the request to the server. (provider: Shared Memory Provider, error: 0 - No process is on the other end of the pipe.)
SQL Server Service is not running. The server may have been restarted, this will close the existing connections, something has killed the SPID that is being used, or it may be a factor outside SQL, such as a load balancer or failover.
Restart the SQL Server Service. Verify any messages in the SQL Error Log.