WE also had this recently, after resorting to reinstalling VSC when our backups stopped working.
The root cause, it turned out, was nothing to do with VSC ...
We're running vCenter on a windows server. It had recently had a packaged version of IE11 installed. IE11 disabled SSL v2.0 and v3.0 in the IE settings. VSC must be leveraging the same crypto libraries, because it too would refuse to connect to some of our storage systems. Frustratingly, all you get is 'the host:port# is invalid' which did NOT help at all in finding the root cause. What did help was using Wireshark and seeing the SSL handshake was being rejected. By comparing with working systems, we eventually found the answer.
To enable TLS, use the command
options tls.enable on