There is a screw in the center of the bar that must be removed, in addition to the screws noted in the instructions for step 4 and step 5. It looks like the bar might go over the screw. It doesn't. The center screw holds the bar down. Remove it.
Step 4-5 There is a screw in the center of the bar that looks like it might not be a hold down. It is. Be sure to remove it along with the other screws at each end of the bar per step 4 & 5 instructions.