Customer with DHCP Internet OK, but VPN doesn't connect

Customer’s network connected in port 4 is DHCP.
Internet wizard passes but not the Talk2M.
Additionally,
MOVED TO STAFF NOTE (38.5 KB)
HMI computer is connected to one of the LAN ports of the EWON COSY131.
Using your publication KB-0068-00 to allow it to come to internet.

The Ewon’s logs show that it’s detecting a lot of interference on one of its Ethernet cables. How long is the WAN cable? Is it shielded? Does it pass by any notable sources of interference?