For some reason the directory for the EMS probe got corrupted by antivirus or by upgrade.
You will see this type message on the portal.log
WARN [AlarmSeverityActor:33] Alarm list is null. (alarms/$Kb)
WARN [AlarmFilteredListActor:33] Alarm list is null. (alarms/$Wb)
Another error that can be seen in the ems log is this:
Probe exception: com.nimsoft.events.common.exception.EMSRestartException: Data Store Open Failed.