For the second time after coming back from a week-long vacation, I opened up AMA to see the "Invalid JWT token" error. The first time this happened, back in October, I escalated the issue with Act support and they ended up doing remote support to fix the problem.
This time I tried to replicate the steps the tech used. When opening the AMA Debug menu I got an "unable to retrieve API" message. Communication with the mothership has somehow been interrupted. Next, I closed Act and uninstalled the Act Connect Link from Control Panel. Then without rebooting I reinstalled Act Connect Link. This time after opening Act and then the AMA Debug menu the fields populate. Communication is back! AMA now is working properly.
I'm not sure what the connection is between AMA being idle for x number of days and the API failing to "talk" to Act HQ but it's obviously there. Just posting this out there in case someone else has this issue. I'm sure it's also a bug that could be addressed in a future update.