I ran into this issue, same error message as above. It might have happend because I took my single user license offline several months ago, but I'm still not sure. I disabled offline use many months back, but perhaps the license did not return cleanly. I randomly got this error message after many months of using AGOL and ArcPro on a daily basis, I did not change settings in ArcPro or AGOL.
The key in my case to getting someone at ESRI tech support to reset my license was to bring up this thread to them. Apparently this glitch its not uncommon. I just wish I could recuperate the cost of dealing with this, took opening multiple cases and most of a day. Just go for the reset if you run into this, don't uninstall/ reinstall software or deal with software authorizations. Just call tech support.
Be nice to have an explanation of what's going on, but it sounds like it may differ case to case. ESRI could add to their current technical bulletin on this issue to make it more clear that its not something that people can fix on their own in some cases.