@Saketo-Nemo I guess it was me đ°
Finally, got the Vo2Max from my watch so let me summarize everything, so we can close this thread.
When I got the watch, I set up every thing and
Did a 15 minutes walk with HR and GPS as instructed (No Vo2)
Did a 10K run on the 3rd day -> no Vo2
Did 10K walk and some other run every other day, all with HR and GPS
During the time I tried soft reset, which did not help, also have done other activities do not calculate Vo2Max(rock climbing etc).
So I factory reset it (about 3 weeks after I got the watch).
Did a 5K run yesterday and a 3K walk
Repeated the same 5K course today and finally got the fitness value on my watch.
As a programmer and technical support person I would assume
Something stuck before the factory reset or
My personal data combine with data from my exercise pattern somehow out range the algorithm and did not trigger the calculation.
Anyway, I finally got it and happy ending is it. Thank you all for the suggestion.
Thread closed.