The steps to place the pulleys on the RIGHT side were backwards. It wanted you to place pulley, belt to other axis, place pully for the other belt...which you couldnt do, since placing the pulley blocks the way!
I had to blink a few times to figure out what needed to be done...place pulley, slide to rear for attachment to moor, place place pulley, loop in opposite axis belt, then another pulley for the remaining belt. Then go back, loosen motor, get belt over pulley
Now I am at the blocks/sliders I think I got it all correct, tho I keep looking at how they tip down/up with nothing in them.