Sync between Android and Firefox not working (but works with Chrome)

Using Firefox 78.0.2 (64-bit) on MacOS Catalina (10.15.5) and Android 8 (Moto Z Play) I can’t get sync to work. I successfully synced the phone with Chrome on the same computer, but I want it to be synced with Firefox.
The error happens after a long wait, where nothing is happening. It says that a timeout occurred. The same exact steps with Chrome work.

So you first synced with Chrome, then unpaired and then with Firefox, without uninstalling the app?
We have not optimised for switching devices yet and there are still some known bugs.

What you can try is uninstalling/reinstalling the app and then sync again with Firefox.
does that work?