The Nexus 7Ks, MDS 9000 series and Nexus 1000v are supported by Prime Infrastructure. (reference)
The error message you're seeing is usually due to a configured transport protocol being invalid for the target device. PI doesn't have quite the wealth of tools to dig deeper in that as LMS does, so I'm not sure exactly where to verify that.
DCNM and PI will remain separate tools for the foreseeable future. They are both under the Prime architecture so they will have similar look and feel but DCNM does a lot of data center-specific tasks that are not on the roadmap for PI.