Hey guys i need help. Have a 2019 corolla hatchback.

Had a curt hitch installed by a coworkers bf. He also did wiring. Hitch is fine but when I plugged the lights I lost lights on the car. Eg. Turn on the left signal works for one flash then lose the rear signal on car and trailer. Front and mirror keep flashing. Turn off signal unplug trailer turn back on and they work again. I assumed he messed things up so I disconnected his work and did my own with same result. It's like the wiring can't support the additional lights of the trailer. Any ideas?