This is associated with the original version of Force Plate (FP-BTA) shipped before November 10, 2023. The redesigned Force Plate Handles (FP-HAN) will work with both versions of the Force Plate.
On some units, the silver plate on the inside of the unit does not perfectly match up with the holes in the outer case. Rather than sending it in for repairs (and paying to ship a heavy object), try the following fix.
Loosen the screws that are in line with the handle you are trying to use. You don’t need to take them all the way out. Once the screws are loose, attach the handle, then tighten the other screws.
This is just like changing the tire on a car–you don’t want to tighten one lug nut all the way before tightening the rest a little bit at a time. If one screw is tight, the rest of the holes may not quite line up.