See attached. This is a fire resistant louvered ventilation window frame and the top section that's giving me an error.

To make it I started with a steel sheet 913x923mm, the full size, then put the square whole in the middle split it at the corners and added the inside flanges. I may have done something out of order because when I save the top and bottom sections and try to flatten I get this mssg, "some bends can't be processed."

Anyone know what's wrong?