Same here, and it's blocking me completely.
What I'm seeing:
Builds process fine and show "Expires in 90 days", but never reach "Ready to Test" or "Ready to Submit"
No Groups column and no way to assign a build to a tester group
The Add button is greyed out from both the group page and the build detail page
I also cannot expire builds any more
What I've tried, none of which helped:
Created a brand new internal group with "Enable automatic distribution" unticked, then tried to add the build to it. Add still greyed out.
Uploaded additional builds with incremented build numbers
In my case it started right after I manually expired an older build that had active testers, so I initially assumed I'd broken something myself. Seeing the reports here, it looks like the same underlying issue rather than anything account specific.
Developer system status is still showing everything green.
Boosting.
Topic:
App Store Distribution & Marketing
SubTopic:
TestFlight