What could cause a published Android app to spontaneously stop working for a large number of users?

Question

I hope this question isn't too broad. I realize the answer to my question is "Anything, it depends on the particulars." I'm just looking for ideas here. I have a published Android app that has been in the store for years. People download it every day. Suddenly, on July 2, 2018, I start getting messages from tons of users, both new and old, saying they can't get past the startup screen, where the app does a series of checks (read-write to storage, check license, etc). I haven't changed anything in the app.

Oh, and of course it doesn't repro for me.

I asked my users for information about the device they're using, their build of Android, their physical location, and I don't see any patterns. It's all kind of devices including official Google devices, and the OS ranges from 6.0 to 8.1.0. Users are from all over the world.

Based on what users are telling me they see on the screen, it seems that the Google Play license check might be the place where things are going wrong. (However, no exceptions or error messages are shown.) Also pointing in this direction is the fact that the free apps (which have otherwise identical logic) seem to work okay.

Did Google deprecate something a licensing library starting on July 1 or something like that?

Any ideas would be greatly appreciated.

Answer 1

Big thanks to @MorrisonChang in the comments to my question pointing me in the right direction. I have confirmed that this was indeed a problem with the Google Play Store app, and customers who upgraded to 10.7.19 report that my apps are working properly again.