ok so heres the situation.... so my brake lights are acting funny... when i turn on the lights on the car the tail lights work. but when i step on the brake only the right hand brake light comes on the 3rd light and the left hand stay off..... i dont think it is a fuse because one light comes on.. and the 3rd brake light is brand spanking new... so its not the bulbs. any other suggestions?

update i changed every fuse and the lights still dont work only the right hand brake light is on