I've tried searching by the serial number, it was in the picture you posted, and also looking for any active devices off your IP address, and the device is not registered in our ACS server.
When a talktalk router is first turned on and connected to our network it should contact our server and register, this will then create a record here so we can see the device. For some reason the device is just not communicating with our server and registering.
As it is not showing up in our database we are unable to connect remotely.
You can try pin reset of the router - hold a pin or paperclip in the reset hole at the back for 10 seconds and this will fully reset the router.
If this still fails to register, then we would not be able to update the firmware.