You have installed a new detection server, all its services are running but in the Enforce console you see that it is not communicating
netstat -ancommand showed that the detection server was not listening on port 8100. Rebooting the server resolved this but the detection server was still not communicating
14.6 MP2 - other environments can be similar
monitor.xxxx.sslKeysStore file had not been copied to the detection server
Copying the key to that location and restarting the Monitor service resolved the issue.
See Symantec Data Loss Prevention Installation Guide for Windows or Linux for more information on creating and distributing sslKeystore files