Front panel shows the following error while initializing:
Connection error. Refer to device documentation for help.
This issue occurs when scanner is switched on without either USB cable or Ethernet cable connected to scanner.
It is an expected behavior as scanner looks for network or USB connectivity first while initializing.
If the cable is connected and still error persist then check for connectivity, check cables/ports and PC should be on in case of USB connectivity.
If all cables/ports and connectivity is found to be normal but still the error remains, then the issue could be with scanner hardware. Contact HP support for further assistance.