WARNING! Don't install beta 14.12 - after update no settings change is possible in GC.

I confirm this. The issue is worse than before 14.12. Now, not only the data screens are impacted, but the whole settings section 

Confirmed. Oh, dear...

Crap I just press install

Edit and I have same problem on my 955

Happened to me, someone mentioned you can re-install GC on your phone or remove the phone from the device list and re-add it. I did the latter which solved it for me, but I had to reconfigure Garmin Pay, perhaps if you re-install GC you won't have to.

Another one bug on 14.12 - see here

i'm lost there

There are workaround to the problem.

You must change your default language on phone to english (my def setting - german) Than this is important! on the watch (your sync not work - haha) go to settings ->System and change language to same language as on phone. Congratulation! Now you can see and edit your fr255 settings :)

and change your language back to your preferred language.

My solution was to forget device from BT setting and then re-pair it  and it did it fine no loss of Garmin Pay. I also deleted and reinstalled the GC app as a matter of course.

The point is not have english as default, but change language to some other on both watch&phone, make a sync and go back.

I can confirm this is a workaround 
Garmin-Kevin This is interesting and will help solving the issue. It looks like this may be an Internationalization issue, for non-english languages.