Had the same problem with mine marie
The strap assembly had broken off with the bolt holes still attached & the assembly was lying next to the speaker stopping the drivers door window from opening fully.
On the outside of the door, you can squeeze one of the metal plates into the gap between the two skins of metal. in the How2, it says to shorten & round off the plates top & bottom. But instead trim off 2-3mm each SIDE. this allows the outside plate to slide between the skins & line up. The internal plate doesn't need much trimming. put the longer bolts through the outside plate, inside plate into the threaded holes on the strap. if the existing metal is badly bent, knock it flat, if not tighten both bolts evenly & the plates pressing together will sort out the bent bits

Hammerite both plates before fitting them.
Colin's Handy Hint - when you are fitting the outside plate, put a screwdriver through the slot. stops the plate from sliding into the door