Often can't sign into Google Play OSS

I’m a bit confused with this one. We’re developing a mobile app which uses GooglePlay to acquire player IDs. Signing on Google Play doesn’t seem to be an issue as everything is seemingly correct.

The odd part is that when released as a Shipping build, the Google Play account which is associated with the same Google account that owns the store/console presence at Google does work reliably. It’ll sign in correctly every time and show the Google Play username and avatar up at the top when Show External UI is called.

That said, every other account we’ve tried across multiple devices does NOT work. Even devices with the working owner account and others have this issue. The one account can sign in, and others cannot. They simply seem to fail and I can’t find any sort of error log anywhere to tell me why. I guess this is a problem in that the shipping builds, which are needed for Google Play OSS, don’t have any logging.

Ideas? I’m pretty confused.