I had the same problem, fooled with it for hours. Then, I decided to put the mattress back on it anyway and the added weight in the right balance, it closed just fine. Try putting the mattress back on and see if it works.
2005 Safari Cheetah 38PDQ - 2009 Ford Flex
Me (Gatogonow), The Boss (DW), Honey Bunny, Maggie May and Mollie Kay (The Gatos)!