I have a sheet metal part that won't flatten, (error message says some bends may be fused, even though they aren't) but being 100% confident that it should, I converted it to a parasolid, opened the parasolid in Solidworks, converted it to sheet metal, and it works fine.
I remodelled the part in a different manner to eliminate the problem, but I still don't see anything wrong with the way it was done originally.
Original model attached
Rick, I ran in to this before the cross bend in the middle of the sketch bends is what caused the problem
when you exported it to parasolid and converted it SW did the side bends as 4 separate bends not 2
with a bend in the middle.