I have a 2004 Volvo xc90 and the brake light on the rear hatch is working but the rear brake lights are not. I was told Brake Control Module, any help would be appreciated.

 

Break lights are controlled by CEM (Central control Module).
Go Volvo Wiring Diagrams download diagrams for your car and start checking wires.
Since you have at least one break light working that means car detects that break pedal is pressed.