Check to see if the connections on the motherboard are loose or unplugged. If the wires are broken, then fixing them will probably fix your problem.

Follow the wires which connect to the speakers all the way to where they connect to the motherboard. Are the speaker grills on your laptop broken? Could something have stuck through the grills and physically damaged the speakers? Look closely for any signs of damage, and try to ascertain what may have caused the damage. If you notice any physical damage to the speakers, like torn cones, then replacing the speakers may fix your problem. If you lack the tools to open your laptop case without breaking it, consider consider taking it to a professional. Some laptops are easy to open, and others are extremely difficult. If you prefer to continue working on your laptop yourself, here's what you'll need to do:

Depending on the design of your laptop, your level of expertise, and whether or not you're still within the laptop's warranty period, you may want to take it in for service at this point. If your speakers still don't work, there may be a physical problem with your hardware.

How to repair laptop speakers