Lead 1515

I have recently purchased the lead 1515 fully loaded. I have been attempting to put it together. I have spent about 5 and a half hours and am only 15 minutes into the video. I am having issues connecting the beam to the assembled gantry plate. I can not get the tee nuts to slide into the slots. The protrusion is facing towards the center of the rail as it shows in the video. It’s almost like the plate is too thick or the screw are a little too short. Any hep on this would be much much appreciated. Also, if I assemble it with the protruded side facing the plate, can that cause issues later on?