The answer to 'my electrical panel won't turn on' is that there could be several common causes, such as a tripped circuit breaker, a faulty breaker, or a problem with the main power supply. Symptoms may include no power to the panel or individual circuits, flickering lights, or appliances not working.
First, check the circuit breakers in the panel to see if any have tripped. Flip the breaker all the way off and then back on. If a breaker keeps tripping, there may be an issue with that circuit or a connected appliance. You can try resetting the breaker, but if it keeps tripping, you'll likely need to call an electrician to diagnose and repair the problem.
If the breakers are all in the 'on' position but the panel still has no power, the issue may be with the main breaker or the power supply coming into the home. This is a more complex problem that requires an experienced electrician to investigate and fix.