Client version unavailable

Hi all,

For awhile I have had clients in my sepm that say 'client version unavaliable'. They also are reporting offline with a yellow triangle. However I know for a fact that some of those computers are on everyday. I've tried to do some research about this 'client version unavailable' but am not able to come up with anything that can really help me.

Currently on 12.1.4013.4013
Manager is 12.1.4a