The event “Backup is not responding” means that the monitoring server does not receive backup progress events from the PC client. These events are being sent out every 10 minutes. Two consecutively missed events cause “Backup is not responding (error) “. The one missed event cause “Backup is not responding (warning)”.
It can be caused by a temporary internet connection issue or interruption of Windows session (the machine gets turned off, fall to hibernate or sleep mode).