When using VPN cannot connect to vcenter ""unable to connect to MKS : ( username /password ) incorrect"

I am on  a VPN , the people in the office can get to this fine , however I am getting the attached error after a log time waiting for it to connect

is this a DNS issue ??

unable to connect to MKS
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
it could be a DNS issue.

Can you resolve the hostname, vcenter server, VM name, by IP address and DNS name (e.g. reverse DNS)

also check firewall ports.

check it happens on all VMs, and not just this VM.
Haresh NikumbhSr. Tech leadCommented:
it is dns issue.

manually added my ESXi hosts and vCenter server IP addresses to the hosts file

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