Question Google Play Services not working and Java Runtime versions

I'm trying to get Google Play Services working for my game and currently it is not activating or authenticating when I open my app in either of a build directly to my phone, or a download from the Play Store via my internal test track.

One of videos I watched with a similair issue suggested changing the app signing key used in the Play Console using the pepk.jar tool available on the Play Store. Aside from still having to setup the environment variables to get this to work, when running the tool I am told that this has been compiled by a more recent version of the Java Runtime, so as it stands I essentially cannot explore if this is a potential option to resolve my problem.

How does one manage this when the JDK/Android Studio etc are installed as part of the original Unity setup? Previously I've set these up seperately and on this occasion it seemed handy to have it as an all-in-one kind of solution, but running into issues for things that should really just work is immensely frustrating.