Hello,
Are all the clients facing this issue??
Could you check 1 of the client machine (which is not updated)?
What is the date and revision number you see on the client machine present?
Did you restarting the client machine / server machine and check if that helps??
Secondly, are these clients taking updates from GUP / LUA / SEPM?
Could you pull and upload the log.liveupdate and sylink.log from the client machine to us?
You may like to check this Article:
Managing SEPM & SEP after vacation
https://www-secure.symantec.com/connect/articles/managing-sepm-sep-after-vacation
Hope that helps!!