I'm reminded of an old saying:
If it doesn't fit; force it.
If it breaks; it needed to be replaced anyway.

I'm tempted to suggest you horse it into position. You can't use it the way it is so if it breaks your out very little. But, before I go that far I seem to remember that old army cots used to shrink a bit in storage and a trick was to dampen the fabric before trying to get everything in position.

Now those old army cots had cotton canvas and once assembled if the canvas was weak it would sometimes rip when it dried. And it looks like your might have nylon so I'm not sure how that changes things. If wetting the fabric allows you to stretch it enough to get everything in position you're golden. If not a few hours in the sunshine the fabric is dry and your out nothing but time.