Check stop light? only one side of tail lights working - no brake lights

Hello, It may sound silly if the answer is 'no', but do you have a towing package installed? Check for power at the brake light fuse, and check for power at the light bulb socket as well. The bulb can be bad even if the filament is good. You can also install a known good bulb from the working brake light into one socket that does not work. If it works, just replace them.