Sorry to hear that. Just in case if it helps following are the list of things I tried but didn't work except for the last method I described.
1) Disable/Enable Web admin on vSheild
2) Enable "http" firewall access on each and every esx host
3) Make sure dns/domain are correctly configured
4) Manually install the vxlan VIB on each esxi host.
None of these things work for me. Except the following
5) Make sure the vCenter Server is operating on port 80.
Good luck!