For whatever reason, trying to connect to a VPN from a domain account that was connected using the VPN has issues:
The requested operation cannot be completed. The computer must be trusted for delegation and the current user account must be configured to allow delegation.
Go to this registry key:
HKEY_LOCAL_MACHINE\Software\Microsoft\Cryptography\Protect\Providers\df9d8cd0-1501-11d1-8c7a-00c04fc297eb
Add a DWORD called ProtectionPolicy
and give it a value of 1.
Copied from https://www.myrtec.com.au/windows-10-vpn-error-computer-not-trusted/