SoftEther VPN User Forum

Hello, first of all I would like to apologize for my noob questions, but I'm not an expert in VPN settings.
I configured a simple VPN connection between a PC running Windows 7 ultimate(SE server) and a notebook, using Secure NAT settings. Both computers are behind routers and with different fibernet ISPs. This configuration works like a charm when connected to fiber net. The problem is when I switch the laptop network connection through a Hotspot (Tethering) and try to connect my Notebook (win7 ultimate) to the server. I constantly receive Error 1 and can not connect. If I switch back network connection to fibernet it starts to work again. My mobile operator does not deny tethering, because I have also an openvpn connection to another openvpn server and it works both on fibernet and hotspot(tethering) connection. So could you help me to investigate what am I doing wrong configuring my SE server or client?

I guess there is carrier grade NAT on the mobile network.
So, NAT-T connection may fail.
Please try to configure port forward on the VPN server side router.

Thanks a lot, that solved the problem :)