I have the same problem with VSC4.2beta. I am running vSphere 5.1. I am able to connect to several systems (Clustered Data ONTAP and 7-Mode) - but I am not able to connect to one of the two 7-mode controller (same HA pair, FAS2040, 8.1.2P2).
Controller 1 works, Controller 2 doesn't. When trying to connect to that particular controller by right-clicking "modify credentials" I do get the error messages "The call failed on the server. see server".
I have the identical licenses on both controllers, I have enabled "httpd.admin.enable". I have also tried it with SSL - same result. I have reinstalled VSC 4.2beta. No clue what could be the problem. What is the troubleshooting path for VSC 4.2 beta? Can I open a call? I have attached the logs of the controller and the vsc.