What SEPM version are you running?
If 12.1, you can click on Disabled, it will open a new window with a better view.
From here, scroll over and you can see status on such things as AV, Firewall, SONAR, Download Insight, NIPS, Browser IPS, and tamper protection.
It is likely one of these is disabled. You can than go to the client and check.
The disabled state is a little misleading. You need to actually open it up to find out what.
It should read something like "Component Disabled" instead.