Factory pattern can return a mock type for testing or a production type, as needed, which makes it possible to unit test the code that uses the produced object.

This quick guide explains it well. Then it improves on it by explaining dependency injection.

https://github.com/google/guice/wiki/Motivation

I have had the same issue a few times. Their troubleshooting page suggests a (not very helpful) workaround: add a shortcut to their webpage to your home screen.

https://proton.me/support/troubleshooting-sending-messages-android

I hope this is solved soon as well. It has led to some unfortunate miscommunication.