Best thing to do is get a test light or a voltmeter/multimeter and take the bulbs out from the back. Turn on your turns and check for power or have someone press the brake and check for power. If no power, then check the fuses. If you're getting power and the fuses are good, then it's the bulbs/connection/ground. Another thing to check is when you pull the bulbs out, look down in there and make sure the contact is in good shape and not pushed down too far or corroded.