Windows 10 VPN only works while TeamViewer is connected
I have a strange case in which the standard VPN-Connection of an employee isn't connecting. Most of the time, the employee is working with our customers, so I used TeamViewer to have a look at the settings of the VPN. Case is: when the TeamViewer-Session is running, the VPN (L2TPD, IPsec) connects to our endpoint like a charm. When I disconnect TV, the VPN isn't connecting at all again.
What could be the cause here? Is TV routing the Windows-VPN? I disabled the Windows-Firewall too, but couldn't achieve any success either.
Thanks for help in advance!