sandrolionetto , I was experience the same, untill I realized the exact path is needed for the authorization.
So when your Mac/user/shared/library/application support shows no folders, you'll probably assumed just as I , that you need the other application support folder to find the personus and personus hub folders, but that's where we're wrong ...
You actually have to make (even if it's the only folder within application support) to create that folder.
So exactly this :
If you're having trouble activating the hub please do this: Manually add path Main HD > Users > Shared > Library > Application Support > (add) Presonus > (add) Presonus Hub if it doesn't exist and then restart the Hub and activate it