I have implemented Firebase Invite with custom email HTML and everything worked fine on my development phone when debugging with Android Studio.
I then built a release signed APK and sent it to my personal phone. Tried sending an invite (to the same addresses as before) and it didn't work - I didn't even get the popup message saying it was sent.
I uninstalled the app, connected my personal phone to Android Studio and ran a debug version of the the same code and voila, everything is working...
What is wrong in release build?