I tried this using chrome and firefox.
Best answer by Lapp Service
You may see Error like "VNC noVNC ready: native WebSockets, canvas rendering Error" or "Connection closed error 1006" (this one could also be resolved by relogin to your PrismCentral)
Looks like the VNC Connections are going throuph PC.
Try to reboot the PrismCentral CVM
(ssh to PC CVM and do "sudo reboot")
Worked for me.