There can be many things that come into play here but, the number one thing is power. If your machine does not do anything at all, the first thing you need to check is your power source. Use a volt meter and make sure you have 230 volts for most sanders, and 110 volts for edgers and buffers. Do not rely on a test light. Check all the way from the source to the machine, check any reset buttons, fuses or other places there are connections on the machine, such as the emergency shutoffs. Wires on cords tend to break near the plugs, so if you do not have power at the end of a cord but do at the source, the solution may be as simple as reinstalling the plug.