Hi!
I just noticed that Forza Hub doesn’t track my Horizon 4 progress. It only tracked 60 Gamerscore but nothing else. I own 9 cars, 2 Properties, completed 3 Horizon Story Chapters, but all of those are at 0 in the Forza Hub 
How long have you waited
It doesnt update immediately
It seems to take at least a couple of days for mine to update
It takes forever for the Forza Reward system to update… takes between 24-48 hours so nothing to be worried about 