I had an issue where suddenly I could not get the settings page for any watch face to open. It would either just spin for ever, or say something like "unable to load app".
The issue, apparently, is that watch face settings require the "draw over other apps" permission. You might have turned this off, for example, if you were trying to get Kiwix to run on your phone. The solution is simply to turn it back on.
For Marshmallow on a Samsung, this is the procedure:
- Go to Settings -> Applications
- Select "Application Manager"
- Select "More" -> "Apps that can ppear on top"
- Scroll down to Pebble, turn it on
On other phones, the details may differ, but hopefully that's the gist of it.
The proper fix would be for Pebble to either not require this permission, or at least give an intelligent error message if it's not granted.