The ride shows in the connect app and logs as being done on the watch for activities but it doesn't update V02 as doesn't show a ride and the endurance score doesn't change 1 point up or down despite 5 hours on the bike?
Unsure in your case - could be one of the delay updates for things like vo2/load - i have seen that in the past. It loads the ride, but many aspects of the reports don't update for it. like it didn't happen... until the next day often. I haven't seen that in a few months tho.
As far as endurance score or training load in general, can be tricky... could have lost a big training load on the old side of things that offset it somewhat? or a hard workout is starting to 'age away' in the oldest week of the calculated data. i haven't been too impressed with that Endurance score either , but i've only had it for a couple weeks... just keeps going down, with my last two weeks being peak weaks for marathon training! lol so... kinda ass backwards.