Anaerobic effect is not loading even if I do more intense workout.

UP.
I think the anaerobic is bugged too.
I'm following Garmin coach Greg 10k plan.
I just went for a run and with 182hrpm (or whatever you say in English :p) I got 0 anaerobic.
Whereas 10 days ago I did one run with 160hrpm and got 2.0 in anaerobic. I don't explain it?
