SEP clients show as offline in web console

SEP 12.1.4112.4156 - Windows 7 clients

I have several clients showing as offline in the server and web consoles but when I remotely connect to them they show online and up-to-date.

I manually update the client (troubleshooting - update policy) just to get it to check in with the server which it does but it doesn't change the fact that it's showing offline in the console.

I've checked client memory and hard drive space which isn't an issue, it can talk to the server, and everything appears to be configured properly.

Any insight as to what might be going on here?

Thanks in advance.