Picked up a Vigor 2710 (the non wireless model)

Factory reset it and installed latest firmware (3.6.8)

Here is a diagram of my setup: WAN (FTTC) --> BT Modem -- RJ45 --> Technicolor 192.168.1.254 (DHCP enabled) -- RJ45 --> Vigor 2710 192.168.1.249 (DHCP disabled, FTP running on port 2021) ---> RJ45 --> Another Router 192.168.1.253 --> My PC 192.168.1.52 (FTP running on port 2021)

So essentially the Vigor is not connected directly to the WAN, it is connected to my Technicolor router which is then providing the internet access.

The reason I bought the Vigor router it is primarily due to the NAS capability. I have a USB drive connected, with FTP and SAMBA enabled and I can successfully connect clients from my LAN to the Vigor and copy/upload/etc, files. All well and good within my LAN.

The problem is when I try to share the FTP server externally over my WAN. I setup the port forwarding on my Technicolor TG582n to forward packets to the Vigor 2710 on port 2021 (this is the port that I have set FTP to listen on in the management page) but when I try to connect to my external IP, the port is reported as closed (canyouseeme.org, ftptest.net/)

My first thought was that the Technicolor was not forwarding the 2021 port correctly so I verified this by running an FTP server on my own PC on port 2021 then updating my Technicolor to forward to this IP instead of the Vigor. This worked and I can see the port is open on canyouseeme.org and connect to the FTP server running on my PC using ftptest.net

So I am pretty confident that the Technicolor is forwarding the packets to the Vigor and this testing suggests to me that there must be something on the Vigor that is blocking the incoming connections on port 2021 and from the Technicolor as a pose to a client running on my LAN.

I have tried (System Maintenance >> Management -> Allow management from the Internet -> FTP Server - tried both ticked and un-ticked both options) but this did not make any difference.

Any ideas please?