Can't Reset TestFlight Invitation

I am trying to test two apps using TestFlight.

I have two separate "feature POC" apps that we publish to TestFlight for testing. One of them is an IAP feature app which utilizes in-app-purchases. IAP documentation talked about the necessity of using "sandbox tester" users, so I've been resetting the user between dev and sandbox user accounts on my phone.

I've accidentally locked myself out of TestFlight access by doing this. I have two apps that I've granted myself TestFlight access, but only one shows on TestFlight on my phone. I've tried revoking and re-adding my account, but it says "Installed" as the status, instantly upon re-adding myself to the app's users. It won't send me another invite, and I can't see the app in TestFlight.

I've even tried redeeming the old code, and it says it's already been used. It WAS used... on this device for this user, but it still doesn't come back.

How can I fix this?