When you install Configs that are for Series X|S via the Beta, that means that you need to use the Beta (since the store version of Manager doesn't understand it). Unfortunately, the only option would be to Factory Reset your XIM and go back to using the store version. Sorry about that, to this day I have no idea why Apple expires TestFlights and worse stops you from using it. It's going to take more than a week for us to get another build through Apples submission process.
If you have a PC, you can use the Beta Manager there. It will required wired configuration, but, it'll get you by until we can get another TestFlight through.