Tailgate opens approx. 5inches and won't budge.

The tailgate is only opening about 5 inches and then won't budge. I checked

-window is all the way down

-window lock up front is not on

-aftermarket rear windshield wiper arm that never goes back in fully on its own is fully in place.

Is there anything else to check before I find a mechanic/body shop?

TIA