Alex, I encountered the same issue in Logic Pro X. It's a bit awkward but there is a method by which it all works as expected.
It appears we can't add and connect any new VE Pro 7 client plugins if in the DAW there is already one such plugin that has been connected to the VE Pro Server at least once. But it works ok for me if FIRST I insert ALL the VE Pro 7 client plugins I require BEFORE attempting to connect any of them to the server, and then I connect them.
Also, if a client plugin has been connected and then disconnected, client plugins added subsequently to that connection will not list any server instances unless and until the previously connected client plugin is deleted from the DAW.
(Logic Pro X 10.4.4; MacOS 10.13.6; iMac Retina 5k, 27 inch, 7700K, 2017)