I encountered a problem with a new AMS. When filament was loaded into the second slot, the first stage feeder assembly would pull the filament a short distance but then the motor would spin freely and make a lot of noise for about a minute before giving up.
I determined that the front roller (near the first stage feeder) was slightly popped out of place on one side, by just a millimeter or so. Rolling it with my finger I could feel it binding a little. The motor may not have had enough torque to overcome the increased friction. I gave it a light push back into place and verified that filament loaded successfully.