L2TP/IPsec VPN fails to connect on Windows 10 or Windows 11- Works fine on iOS
I was finally able to resolve the matter after making an edit in the registry and then rebooting.
Run the following from an elevated command prompt (make sure you run it as administrator):
REG ADD HKLM\SYSTEM\CurrentControlSet\Services\PolicyAgent /v AssumeUDPEncapsulationContextOnSendRule /t REG_DWORD /d 0x2 /f
Also, make sure, the following conditions are met:
Reboot Windows and you are good to go!
It also works great on Windows 11!