I had a lot of these problems myself. One thing that helped was getting both of us on the same version.
My friend (performer), only being new to Cubase, had assumed that because VST connect pro 4.0.42 was listed in the download assistant that he had it installed. As soon as he installed the same version as me that solved a few problems.
Getting the studio side of things loaded up and logged in before the performer starts up and logs in seemed to help.