1. Check the fuse. The cigarette lighter sockets are likely powered by a fuse, which may have blown. Check the fuse box in your vehicle's owner's manual to find the fuse that controls the cigarette lighter sockets, and make sure that it is not blown. If it is blown, replace it with a new one.
2. Check the wiring. If the fuse is not blown, then the problem may be with the wiring to the lighter sockets. Check the wires under the dash to make sure they are secure. Look for any obvious signs of damage, such as loose or frayed wires. If you find any damage, you may need to repair or replace the wiring.
3. Check the cigarette lighter sockets. If the fuse and the wiring are both intact, then the problem may be with the cigarette lighter sockets themselves. Try plugging a different device into the sockets to see if it works. If it does, then the problem is with the original device, not the sockets. If it doesn't work, then the sockets may be faulty and need to be replaced.
If you are uncomfortable working on your vehicle's electrical system, or if you cannot find the problem, then you may want to take your vehicle to a qualified mechanic for diagnosis and repair.
