SOLVED - How is a new build in a release channel installed?

The solution, make sure the Bundle Version Code of your submitted APK is a step ahead of the version you have uploaded to your device via a USB connection.

I have uploaded a new APK to my Beta release channel but my users have not been notified and there is no way to install the new version manually. I don't appear to be able to uninstall the previous version from my own library using the GO.
If I try to view the details of the app on the mobile app it crashes.
What a mess!
Has anyone had similar issues?