Anyway to override being locked out of ArcGIS Pro which was set up for offline use?
Travis,
Offline license of ArcGIS Pro will remain on the computer until you return the license. Otherwise AGOL will continue to prompt the error you mentioned above when attempting to log into Pro on any other system using that account. I understand you've been using just the one machine. These are two scenario which may have occurred:
1. You logged into the system using account A and took the license offline. Then later you logged into the system using another account, B for example. Pro will start with the default AGOL login page because the offline license only applies to the Windows users it was taken offline for. Of course you're attempting to log in with the same account. Again AGOL let you know licenses were already taken offline for this account. If this is the case, log into the system using the same account you used to take the licenses offline. Then proceed to return the license.
2. At some point you've attempted to return the offline licenses and failed or something odd had occurred where the borrowed licenses became corrupt. The machine no longer acknowledge there is any borrowed license. But AGOL says otherwise. In this situation, you will need to contact our Tech Support or Customer Service to reset the account at the AGOL side.
Hope this helps. 
I ran into this issue today. Over the weekend I was experimenting with my work laptop at home; decided to check the box for offline use. Fast forward to today, middle of the work week. Was having unrelated, non-GIS issues with the same laptop, so I decided to re-image the machine. Lo and behold when I reinstalled ArcGIS Pro I was prompted with the following error message after entering my AGOL username and password. Called ESRI tech support and they were able to reset the license associated with my AGOL account.
