tail light wont come on

Did you test the electrical circuit for power at the bulb socket(s) using a test light ? Was the bulb(s) you put in any good ? Did you push the bulb(s) into the bulb housing(s) all the way ? Was there too much di-electric grease inside the bulb socket(s) for it to operate properly ? Where the connectors inside the bulb socket(s) broken, damaged or in need of cleaning ? Did you make sure the ground for the bulb socket(s) was connected properly ? Did you check all the fuses for the taillights ?