It was Marketpress Version 2.9.5.1 and I was using WordPress 4.0
This is when it worked well
I am having the same problem. I installed marketpress before the last update. it was working fine and I had the store dropdown on the main menu. I updated to WordPress 4.0 and it worked fine. When I updated the Marketpress plugin to 2.1.5.3 the store button on the main menu turned to order status. The only way I was able to get the store button back was to add more items to the menu.
Is there a problem with the Marketpress update or is it not compatible with WordPress 4.0?