If it’s a cable one the tension on the cable could be wrong or kinked.
I’d take the remote off the bars, pull some cable down to the bottom of the frame and lift the dropper out. You should find it works.
If that correct pull the cable down through the tube whist you put the post back in the frame, adjust the cable in and out of the frame tubing if it still does not work.
Mine had a kink in it from new and I had to cut abut three inched off the outer.