Using Bixby with a Garmin Smartwatch

[rsbrux]

I have a Garmin smartwatch that supports various voice assistants, including Bixby.

I have enabled the watch to use voice assistance and have configured Bixby according to the instructions in this FAQ article, but it doesn't work.

If the phone is locked, the watch says, "First use face recognition to unlock the device" (even though I have enabled "Use while locked" in Bixby's settings on the phone).

If the phone is already unlocked, it sometimes works, but sometimes the watch shows that it can't connect to the voice assistant.

What else do I need to do to be able to use Bixby on the watch, even (and especially) if the phone is locked?