I think I have figured out why we weren't getting the alpha releases through the normal channel. Apparently GP remembers the groups you were in at the moment you accepted the conditions.
Please try going to
https://play.google.com/apps/testing...calibreandroid
and selecting "Leave the test". Wait some time (10 minutes or longer) the go to the URL again and join the test. When I followed these steps I saw the alpha version in the GP store in minutes (
https://play.google.com/store/apps/d...eandroid&hl=en)