If your scanner is not working and if it given error like "Communication Error with Scanner..."

Probably the IP address from your printer/scanner changed. It was no communication with the scanner possible anymore.

You can easily change the IP address in the printer settings, but not in the scanner settings. 

The solution of this :

goto Start->Run->regedit 

goto HKEY_USERS\S-1-5-19\Software\Hewlett-Packard\DigitalImaging\NetworkScanners\083E8E8A89D7

right click to right panel Add->String Value->IpAddress

Double click to IpAddress and enter IP address of your MFP or HP scanner like 

If it is not in S-1-5-19  try others  S-1-5-18 or S-1-5-20, etc