I can't pick up anything...

Hello even though everything is connected properly, have you checked for standing waves on the antenna to radio connection? Also you may have to perform a sensitivity test on the unit. The problem is you need a RF generator for that. Set you RF generator to the frequency that is equal to the CBs middle frequency and modulate the CW with 1KHz at 50% modulation, tune to the middle of the CB band on the radio and set the output of the RF generator to .1uv and loosely couple the signal to the CB antenna with a loop of wire. Your CB should be picking up a 1KHz tone gradually turn the power level down and when the tone cuts off that level is cutoff level, then increase the level until you can hear the tone again when the tone cuts on that value is the sensitivity of the unit. Compare the measured value to the value in the owners documentation. if the sensitivity is low this could denot a problem in the RF/IF section of the CB.