I bought a Vigor 2865Lax-5G and I am trying to connect VPN dial in establish a connection using VPN Matcher and OpenVPN when it's SIM card/LTE mode.

I followed Draytek's advice for the settings and referred to the following URL.
https://www.draytek.co.uk/support/guides/kb-openvpn-host-to-lan-vpn-matcher

But I cannot establish a connection with following erroe "The remote access server is not responding"
If anyone has used SIM/LTE mode with VPN dial-in, could you please advise how you set it up?

Did you get this working? I am trying VPN Matcher with SmartVPN/OpenVPN & getting the same error. My Vigor2862Ln has a Community Fibre WAN, which like your 4/5G is behind CG-NAT.