VPN Issue - SSTP

[SimonInOz]

We use a VPN to connect staff in to our campus, and yesterday when at home, I got the following error:

 

'A required certificate is not within its validity period when verifying against the current system clock or the timestamp in the signed file'

 

My system clock was fine, and was syncing with an external NTP source.

 

We use SSTP to connect, and I am having trouble locating the actual certificate. Can anyone assist in troubleshooting this, and working out whether this is an expired (etc) certificate error, or something else?

 

Many thanks