Hi Tom,
I'd make sure that the config is enforced = NAC is green in NAC manager and no yellow flag icon.
Then in NAC manager click on the client in the end-system tab, right-click and choose "configure evaluation tool" then "run evaluation".
Here you'd see why rules have no match, might be a good start to troubleshoot.
At least I use it all the time if I've a authentication issue or clients get the wrong role.
-Ron