Activity rings disapearing from Apple Watch

I have an Apple Watch 6 and are using the display with activity rings (calories, training time and time standing upright).

The activity rings keeps disapearing after a few hours. I still have the numbers, for exmple how many calories I have burned but the rings are gone. If I restart the watch the rings come back but then after a few hours they disapear once again. This did not happen on my Apple watch 5. Anyone have any idea what's causing this?

/George