I'm sorry for the frustration. The following might help...

If you're comfortable navigating to a hidden folder, can you

1. Close ProSeries

2. Rename C:\Users\{username}\AppData\Local\Intuit\Common\Authorization\v3\Data to C:\Users\{username}\AppData\Local\Intuit\Common\Authorization\v3\Data_Backup

2. Restart proseries and login. You might get a different "client_invalid" type error. If so restart ProSeries again and then login. It should create a new Data folder and I think you might be ok after that. 

Also, whether it fixes it or not, can you send C:\Users\ocardoso\AppData\Local\Intuit\Common\Authorization\v3\Logs\IntuitAuthLog.txt to me at proseries_engineering@intuit.com?