These sites always seem to suffer from the same problem - not enough contributing members. It's quite understandable - what is the incentive to post a problem? What is a chance that someone will solve it? When will it happen? How will I know about it? etc. All these factors result in a situation in which people rather treat such sites as an entertaining curiosity.
My suggestion to improve it is: make it an inverted Kickstarter - if I've got a problem I pledge X dollars for someone to create a solution for it. Other people with similar problem add their pledges. When the sum starts to look tasty developers pick up the challenge and compete (?) for the bounty. The backers get the solution at discounted prices. Everyone's happy and live long ever after ;)