I had the watch3 and if I was inactive for a while it would nudge me and then give me some stretches to choose from.
The grey dude is indication the hint app has crashed and locked up
I have reported this here before but god knows why
Galaxy Watch 4 - My UK Bad Problems So Far - Samsung Community
the only solution is factory reset but it re-occures in a day or two
UK here I dont evben get FW updates that others get I should have know better