This is the first time I decided to use testFlight. I uploaded the build through XCode, it was processed with an issue. Currently it is on 'Ready to Submit', but when I am adding external testers it results in an error "There was an error processing your request. Please try again later." I tried to produce another version and re-submit, but the same issue is present. Internal testers for this app, receive an email that they can install the app, but when they press 'Install' they get an error message saying that "Required app is not available or doesn't exist".
If anyone knows how to fix this issue, please let me know. Much appreciate your time!