It takes time. You can’t throw a group of strangers into a room, tell them to trust each other and then ask them why they don’t. These people don’t yet have any kind of investment in your community (or in you) so what incentive is there for them to try and troubleshoot for you?
The two important factors are time and value. Unless you are fixing a problem or fulfilling a need people aren’t going to prioritise spending time on your community. Think about the communities that you belong to. They either solve an immediate problem (here you get technical help to get your forum up and running) or fulfil a need (Facebook helps you stay in touch with your friends and feel connected). You need to have a very clear “why” for your community. Without that you will never succeed. So that’s the value part.
The time part is one that people struggle with. Communities can take up to a year to reach critical mass (the point at which they become self-sustaining). Start slowly with a small group. Build trust between them (and you) and then grow slowly.
Start building relationships in order to create your beta group.
Actually, this is a slightly updated version of the model I linked to in my last post. It has some extra info.