unable to connect with l2tp or ikev2

[jiang shanming]

Hi, developer, I've been in trouble making l2tp or ikev2 connections with the windows 10 built-in VPN ever since I installed openconnect with the windows GUI. Now I have uninstalled the software, but error 720 keeps occurring when I try to establish l2tp VPN connection and it says I need to change the network settings. I'm not sure if openconnect changed any of the system settings, which might lead to the problem. I manage to connect with l2tp with the same VPN server and account on other devices (windows and android) with the built-in VPN, so I guess there's nothing to do with the VPN server. Is there anything I can do? Thanks very much!