Hello,
If you can load and unload filament from the external side and run it through the internal buffer, then the printer should be working fine.
Are all the slots on AMS Pro 2 not loading, or is it just one?
Just one slot check that feeder unit they might have a filament sensor on the grey lever arm. See if there’s any filament buildup in there remove the sensor to inspect.
You could also disassemble the AMS hubs and check the filament sensors. Look for any filament buildup, and remove the sensor to inspect it more thoroughly.