Sounds like you are not getting power to the Toad brake lights.
First I would check for power at the plug to see if you are getting power to the umbilical cord. I not problem is at the MH. If you have power connect the umbilical cord and check for power at the toad end if not power find the break and repair. Next you will have to test the toad from the plug to the lights and do not forget the diode.
I tried to make it short I hope this helps.
You will need a test light or Volt meter and a ohm meter to run this test and an assistant.