I know this sounds crazy but try different bulbs…we had a electrician for a couple new light bulbs that would flicker or not work in the kitchen…electrician put other new bulbs in and worked perfectly. He said very often new bulbs in a package may be defective…they work great now!

Some things mentioned so far have important omissions you need to know about.

The main circuit breaker does shut off power to the entire house. It does that by shutting off power to the rails that al the other breakers plug on to. There is still power in the breaker panel that can kill you. The power feed coming into the panel, connected to the main breaker, is still hot.

A tripped breaker may look like it is in the on position. But it will be slightly off the fully on position. To reset it, push it completely off, wait 15 seconds, and push back to the full on position. It will clunk. If it trips right away, you are done, call an electrician to fix the short.

The easiest way to troubleshoot this is with a volt meter. That will tell you what voltage is present.

There are non-contact devices that will beep and (most) light up a led to tell if power is present. It does that by detecting the field given off by live wires.
If it indicates, then you have power somewhere near. Depending on how things are wired, it might be a nearby circuit, or the circuit you are expecting.
If it does not indicate, it says power MIGHT NOT be present. Maybe you are too far away? Maybe voltage is low due to a bad connection? You must be sure it is really working properly. Test it on a known live circuit (another outlet, lamp wire, etc) and see that it works. Then retest the thing you first looked at. And retest on a live circuit again. Only then is it possible that power is off there. Now use a voltmeter to confirm.
The normal use for it is to warn for power unexpectedly present. Also a quick way to find the right breaker; first see power is present, then trip breaker, and see power is now off. Good electricians will always recheck with a voltmeter for safety.

Not all dimmer switches have lights on them. Remember, light on means power is present. Light off does not mean anything. What if the light or switch is defective?

Replacing a breaker is easy. Take off panel cover. Trip off the bad breaker. Measure with a voltmeter. Unsnap from back plane then disconnect wire on it. Put wire on new breaker (of correct make and same amp rating) and torque screw to specifications. Be sure breaker is off and snap back into panel. Turn it on.
Don't touch other wires or any part of the back plane where the breakers mount onto.
Some people trip off the main breaker to make it less likely to contact live power.
If it's a GFCI or Arcfault breaker, there will be another wire from the breaker that needs to be removed and the new one reconnected.

AC voltage in your house causes an interesting action on your muscles. It makes them contract. If you grab a live wire with bad insulation, your hand squeezes harder on the wire. Likely you cannot let go. You might be able to launch yourself away with your legs if you are lucky. A friend with you might grab you to pull you away, and they could get electrocuted too. That can be wiring in a breaker panel, lamp, outlet, or a light switch.

Fixing this issue is not a complicated process. Taking off the breaker panel cover to fool around inside is not a job for a novice. Not much you can do inside without first using test equipment to see what is really happening.

If you are having troubles in more than one circuit, you likely need an electrician. If it's several circuits, you absolutely need an electrician. What is common to multiple circuit problems? The main power feed, main breaker, breaker panel itself. None that a homeowner should fool with.

Led lights don’t always work with some makes of dimmer switches.

Thanks for all that information. Should help people also dealing with something like this!

OP, I have done a lot of DIY projects over the years. I even built a room addition once. I have run wiring, replaced wall switches, wall outlets, and installed light fixtures and ceiling fans. But, I would never do anything inside the main electrical panel, except turn the circuit breakers on and off. I would hire a licensed electrician for any work in the panel. To me, it is too dangerous and too much of a risk that you will violate the electrical code. I wouldn't even hire a handyman. Just my opinion.

I never saw where you said you changed the light bulbs, even LED lights burn out. Have you changed the bulbs before you checked breakers etc. I have changed or added many breakers over the years. The hardest part it the electric box cover is heavy. Unless it is a ground fault breaker you just pull the old breaker out and plug the new one in. To be safe shut off the main but you can do it with the power on as well.

Not trying to be sarcastic, truly not mean this in that spirit, but I think you might have missed the object of the post completely. If you give it another read, the person is not asking IF he/she should or should not call an electrician at all, in fact, STATES CLEARLY they probably will, but was asking for an explanation of the whole breaker situation.

Great advice to do the trouble shooting !

You have that right. I bought a 20 amp circuit breaker at Ace Hardware and was wondering if I can just shut down the power and take out the old circuit breaker and put in a new one without worrying about wires? It does not look like it. I have flipped that circuit on and off a number of times but it has not resulted in any electricity getting to the switch. They remain dark.

Our model has the same setup, ONE light directly over the sink can be turned on separately with a different switch, and we have had quite few switch failures over the years (maybe they "don't make um like that used to" ? LOL !). At least that is a simple, easy task. Hope that's your issue !

As I understand it, you need to remove the electrical panel cover, turn off the main panel power switch, remove the defective breaker, disconnect the wire that is connected to the breaker, connect that wire to the new breaker, and then plug in the new breaker. So, yes, you do need to worry about wires.

But, the first thing I would do is to remove the wall switch that is not getting power, and replace it with a new switch. Very easy and inexpensive. It may solve your problem.

Thanks. That is a good suggestion.

It's not just a matter of turning the breaker off and then back on. Once you flip it to off, you have to continue to push toward the center of the panel as far as it will go. You'll fill it sort of springy. Then flip it back on.