Ok, rear lights........are you replacing 5/21watt bulbs? If yes how did you test them...did you turn on lights and then press brake? Maybe bulb is fitted wrong.
How I would fit;-
Turn side/tail lights on.
Fit stop/tail bulb noticing intensity of light, remove bulb and rotate 180 degrees then refit noticing intensity of light..........the bulb will be brighter when the brake light circuitry is energised........so refit the bulb so the light is less intense, do the same for the other side.
Then recheck operation.
If the lights all worked before there's no reason why they shouldn't work with LED bulbs....IMHO
...checked your fuses?