Thanks!
Got it working...
I changed the version code for my next revision - per my standard procedure (start a new version after apk was uploaded to google play). Once I uploaded the new apk all worked as expected again.
Interesting discoveries and tips through my working with Google Play Beta testing:
You can do full debugging on your device and everything works fine AS LONG AS THE VERSION IN GOOGLE PLAY AND YOUR DEVICE IS THE SAME. You can test changes with a local install and google play comms will work the same.
Once you're happy, THEN change the VersionName and VersionCode before uploading to Google Play.
Also, an app can have both in-app purchases and subscriptions active. I wrongly thought that it could be either, not both. Fortunately, I was wrong and you can have both.
In-app purchases AND subscriptions can be tested without charges IF THE TESTER'S GOOGLE ACCOUNT EMAIL IS SET UP IN Console > Account Details > License Testing AND in the Beta Test Group in Console > Manage Testers.