If you’re talking about Discourse’s SSO module it’s meant for people to write their own integrations. Pointing it at Crowd won’t work because Crowd doesn’t implement our SSO specification.
However, we do have an official Crowd plugin that has been used by some of our customers. If you install that plugin in your Discourse, you can configure it to allow users to login via crowd and retrieve their information. I think that’s more along the lines of what you want to do!