Vo2 Max

Hi there! I run or walk 2-3 times a week with my vo2 max results always showing right after in the health app. After my last 3 runs…nothing. Shows my last run was Sept 21st when I’ve ran 3 times since🤔 My vo2 max results have started to become wonky too, a difference in 5 or so whole points which is odd since Ive always been very consistant🤷🏼‍♀️ Anywho, more confused about it not showing at all the last few times. What could be going on? And yes, Ive checked allllllll my settings, havent changed anything recently. The only thing I can think of is that my watch automatically updates a few weeks ago.