Issue with Device Tracker

Configuration
1

Hi, I am new to HA, I am just getting to grips with how it works.

The first thing I have tried to do is to setup Device tracking, I have one of the approved routers (a Technicolor) which HA says should be setup as a Thomson.

I have the following in my configuration.yaml file

device_tracker:
  - platform: thomson
    host: 192.168.1.1
    username: admin
    password: Password

The issue is that HA is not automatically creating the known_devices.yaml file. Is there a way to see if HA is talking to the router?

Regards
James