You are unable to connect a detection server with Enforce server after rebooting it. You've already tried:
In this instance there was as software corruption after Windows patching was applied.
The boxmonitor_operational_0.log on the affected detection server showed that sub-services (Filereader/Aggregator etc) do not start and no message such as the one below is seen:
Detection Server status changed from STARTING to ALL_RUNNING
In this instance the detection server was reinstalled.