The Backup is not responding event means that the monitoring server does not receive backup progress events from the client. OBRM sends the events of this type every 10 minutes.
One missed event cause result in the Backup is not responding warning.
Two consecutively missed events result in the Backup is not responding error. This can be caused by a temporary internet connection issue or by an interruption of the Windows session, that is if the computer turned off, hibernated, or went to the sleep mode).