My alternator is not charging my battery. Battery is just under 2 years old, serpentine belt is fine, checked fuses, I took out the alternator and I got it checked say that is at full health. What else could I be missing?

Car has 170k mileage

 

I would check the clutch on the alternator pulley, it might no longer be engaging and thus although it spins, it doesn't produce current.

How did the shop check the alternator? You should be able to spin the pulley and attach a multimeter to the positive terminal and verify it produces current, then do the same with it installed. If it's producing current at the alternator end, check the battery end as well. If no current there then it's likely a problem with the battery cable.