Unable to process request - Server or Network error, this usually indicates some network disruption (like wifi disconnect or temporarily unplug the network cable). On a network disconnect, client will not be able to reach the server and hence that pop-up which indicates the user that the connection is lost. This is informative message. Note - if it only happens for one user or very infrequent this should not indicate wider issue, if it's something in continuous please open CA Support case and we will investigate.
This is usually accompanied by HTTP status code error in the app-ca.log files.
ERROR 2018-09-22 04:14:15,293
OnError called--Client Side Exception
java.lang.Exception: VXMLRequest failed. HTTP status code was: 0...