4.5.0.16 Signal shows warning: "Dauerhafter Signal-Kommunikationsfehler"

[theseer]

You need to update the fake store as described here:

[4.5.0.16] Signal Android with MicroG complains about not being able to register with play services

How did you install it? From F-Droid? If so, locate “FakeStore” in F-Droid, scroll down to “Versions” and select version 0.1.0, by default 0.0.2 gets installed. If you installed it from somewhere else, make sure to install version 0.1.0 of FakeStore by whatever means.