Tail light problems

Most likely a lost connection in the signal switch contacts. Those contacts change the current path the rear bulbs from brake to turn.
If you have a wiring diagram and locate the signal switch connector under the column. Brake light power goes in on off white when that switch is closed. You could press the pedal or poke a cotter pin in it from the back side as a jumper. The same current should come out on green and orange to left and right rear. Signal switch should interupt one or the other and send turn signal current intead. A failed contact in the switch goes no power no way no how on one of those 2 wires.
I forget right now which is right or left green or orange. You can look in the trunk and see.