Why won't the camera come on even after changing batteries?

Could possibly be bad batteries. Have they been sitting out of the camera for a long time? If the answer is yes then they are likely bad and will need to be replaced. Letting lithium-ion batteries sit for long periods of time without charging them will cause them to drain and once they drain too much it does permanent damaged to them and they will never charge back up again. It could also be a problem with your charger for your batteries. If you have a volt meter you can check both the batteries and the charger. If it’s not the batteries then it’s probably something electrical with the camera.