Adding External Testers shows No Build Available

I am trying to add testers to External Tester groups for a couple of our iOS apps and after adding them it shows "No Builds Available". This is despite the app being available to that External Tester group with other people having already installed the latest version of the app which is "Available" and not expired.

Can someone please fix this? It is so frustrating the number of times I try and release apps to TestFlight and there's some issue blocking me, completely out of my control and I have to rely on someone at Apple fixing something on this terrible AppStoreConnect system.

I am also experiencing this issue. Is there any known workaround or alternative solution available?

Adding External Testers shows No Build Available
 
 
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