Apple Watch not recording activity

I have an Apple Watch Series 4. The watch has stopped tracking my activity-though my phone is still recording activity, so maybe it’s just the readout that’s screwed up?

I’ve paired/unpaired, reset, turned both devices off, etc. Doesnt seem to solve the problem. I did wear it while floating the river on Saturday. But the watch continued to function fully for a good day and a half after that so not sure if that’s a factor. Activity tracking was my whole reason for purchasing the watch so this is a bummer. Help is appreciated!