I have also faced this issue before , make sure you are accessing the IP correct if you have multiple VRA in place , don't use the load balancer IP here.
If you are getting same results as you mentioned , recommending to change root password , for this power of VRA first then from "VRA edit settings -> Options ->Vapp Options - properties "
Facing the same problem, but I solved it, maybe (it's still maybe) it's the port problem.
There's firewall between my PC and the VRA server, I can access the vra:5480 from my PC, but when I try to login I got the same error "Invalid server response".
So I try to loggin from my iaas server (which doesnt have firewall between vra and iaas) everythings good.
I don't know yet what port it's need (should be some port to the SSO server), I'll check it later.