The detection server is being recorded in the Enforce under "Servers and Detectors" as upgraded to the new version but appears Unknown, with a question mark.
DLP 16.1
Warnings will be reported in the Enforce MonitorController logs stating keystore creating failed. Additional warnings may be seen after each SymantecDLPDetectionServerControllerService service restart
Example:
WARNING: An exception has been thrown while updating the cache DetectorConfigDataObjReference
Error: Failed to auto provision the <hostname>-<monitorID>-<ID> keystore for component EPS. Error:Failed to create keystore
Contact your DLP Support team for assistance in resolving this issue.