vcenter inaccessible

Hi,

Suddenly my vcenter was inaccessible, though IP is still pingable and I can see the login screen since it's a vm to a host and I can open a console to look at it.

So far I've reboot the vm and host but same thing. Not sure where to go next?

Some added info:

I'm using VCSA 6.7

Both hosts connected to vcenter and it was working before but yesterday when I turned on 2 hosts and the vcenter vm, it's unable to access the web gui of the vcenter

Thanks

Jeff