I pair it with my Android phone. It’s successful but then immediately get unpaired. In an endless loop
I’ve just realized that this phenomena relates to my Sony Xperia Compact X. I guess an update a few months ago is causing this. I tried to pair the watch to an old Galaxy S4 and it’s working fine.
So something in the very advanced Android OS is bad for my Pebble.
I found the solution:
Have to disable battery optimization for Pebble app.