Help....3rd brake light

[5pt7art]

Hey guys I installed a cargo lamp off of a 2020 powerwagon into my 2011 ram single cab... don't need the camera.....brake light works fine....cargo lamp works fine....but when truck is on.... the cargolamp portion just flashes....any ideas??

 

[5pt7art]

You can see the light on here....they flash like strobes......