internal network <-> Sophos UTM <-> external router <-> internet = cannot make VPN

Hi,

recently a telekom provider changed their router through which we receive internet. After the change, I cannot establish a VPN connectivity, neither SSH connect through VPN client.

I have the following configuration:

internal network <-> UTM (used for firewall and VPN connections) <-> Telekom router <-> Internet

UTM eth0 172.20.101.0/24 connected to internal switch

UTM eth1 192.168.1.2 connected to one of the Telekom router switch ports

The Telekom router connects with PPPoE with the internet. 

Telekom router IP is 192.168.1.1

Telekom router DHCP 192.168.1.2-192.168.1.200

I configured a static IP address 192.168.1.2 for the UTM bound with the UTM NIC MAC address.

Currently, my local computers are connecting to the internet and I can make a teamviewer connection to one of the computers from the local network.

But, I cannot make a VPN connection, neither connect with the Sophos VPN client.

Can someone advise how to resolve this issue?

Thanks in advance!