Sounds like it's simply a bad switch if you're talking about the normal headlights. If it's daytime running lights there is a "kill switch" in the handbrake that turns them on when the brake is released and off when the brake is activated.
If the lights come on but do not flash, replace the flasher relay. If they will not come on check the fuses.
First check the bulbs then check the fuses.
you could have possibly bought the wrong bulbs and/or fuses. or when you were replacing them you may have damaged the wires. Also the reverse light switch may be defective.
Flasher relay is bad if the lights come on but do not flash. If they lights do not come on at all then the bulbs may be blown or the fuse if blown.
Faulty bulbs, faulty switch, faulty wiring, disconnected ground.
sounds like you need new taillight bulbs
check your fuses first, if none are blown, check the bulbs if none are blown, then take it to a shop you've got a wiring issue.
Check the fuses first. Your owner's manual should tell you where they are. Most likely its the fuse. If not, check the bulbs because on some vehicles a bad bulb may break the entire circuit. They are separate circuits, separate fuses and separate swithes. Check the fuse and the tail light bulbs.
Check turn signal switch. Pull back lighty on turn signal lever and brake lights will come on. Replace switch inside steering column. The green and yellow wires you see at the bulbs are the ones that control the brake lights and turn signals.
Check the fuses.
First check if bulbs and fuses are good and see if the back lights come on when you turn on the lights. If everything works and the bulbs and fuses are good then its most likely the brake switch on your brake pedal, its usually the only thing wired to the brake pedal. If its not that you might have a short somewhere but usually its either fuses or the brake switch, both are cheap and easy to change.
There is a switch under brake pedal. This switch controls the brake lights. They some times go bad. Have someone stand behind vehicle while you push on brake pedal, if no brake lights come on. Try pushing the brake switch by hand. Check for power with a voltmeter.