Showing generic error when adding new build in TestFlight

I have done the following after receiving an approval for my app:

1) Create a new testers group

2) Click on the group that appears on the left

3) Click on the Builds tab on the right side

4) Click the Plus sign and select the build

5) Click Next, fill in the details and click Next again

6) In the Testing Information - fill in the text field and click Submit for Review


Now I receive the generic error "There was an error processing your request. Please try again."

I am practically clueless as this generic error does not even give me a place to start checking what is not working here.

I'd appreciate assistance.


Thank you.