I know this is an old thread, but I'd like to share a new development.
My floor counter stopped counting, and the barometer sensor wouldn't give a reading anymore. A watch reset or app update didn't solve the problem.
So I thought the barometer sensor was broken and had it replaced under warranty.
It worked fine for a few weeks after repair, but then again.... same symptoms. With the new firmware update coming I decided to wait with having my watch repaired again, to see if it is a firmware issue.
And then I read
this post on xda, today.
I changed the floor objective to 5 (but the number is not important, changing the objective is), and my watch started counting again.
Victory!
Now let's see if it holds.