I am guessing you mean 'SnapCenter' Plug-in?
Anyway, if you mean "NetApp Virtual Storage Console (VMware) 4.2.1" ? , then max supported version with this plug-in is : vCenter 5.5U2.
If you have SnapCenter Plug-in 4.2.1 for VMware vSphere, then : vCenter Server 6.7U3 is supported.
If you are NetApp customer, you can verify these components here: