The arm has a 'lift' mechanism. (that's the 'L' in the model number)
The lift is the curved black plastic near the pivot.
It has a screw, and is hard to set properly. Most likely the lift is set way too high, so it cannot lower at all.
Try releasing the screw and allow the bar to slide all the way down.
If the arm then pivots up and down ok... Then all you need to do is adjust the lift properly.
If the arm will still not pivot up and down, some other thing is binding it
The lift is the curved black plastic near the pivot.
It has a screw, and is hard to set properly. Most likely the lift is set way too high, so it cannot lower at all.
Try releasing the screw and allow the bar to slide all the way down.
If the arm then pivots up and down ok... Then all you need to do is adjust the lift properly.
If the arm will still not pivot up and down, some other thing is binding it