Wanted to replace a switch with a dimmer. Took off the old, put on new, lights will not come one. Checked with voltage meter, we have power. Decided it may be a fault with new dimmer, put old one back on, no lights, again we have power, lights were on before we started the process. Bought another new switch, again, lights won't come on. All outlets working. Light in shower area working, all on same breaker, only the lights over the sinks, grrrr. Thought we would surprise our daughter with update, this is not the surprise we want her to find.

The lights are 8 lights across top of mirror if that means anything

Have there been any modifications made to the electrical circuit since it was originally installed? Are any of the receptacles near the sink or in the room ground fault circuit interrupt (GFCI) type and have they been connected into the light circuit? Light fixtures and receptacles are not typically connected on the same circuit breaker. Check and make sure all GFCI receptacles have been reset if they have tripped.

When you removed the original on/off switch, how many wires were connected to the switch- Two conductors and a ground? or just two conductors? Make sure the dimmer has the same wiring configuration.

If all else fails you may need to call an electrician. You don't need to take chances with power and end up burning your house down.

A switch is a switch, is a switch, is a switch. The only difference with a variable switch is that it regulates the voltage to the switch by way of resistance.

What is unknown is how the switch is connected into the circuit. If the switch is connected via a switch loop, then you should have found a white/black cable going to the switch. This method uses White to feed the switch (I usually feed on the bottom) and Black to return the voltage to the light.

The other way is to bring power to the switch. This can be identified by the White (Neutral) just by-passing the switch and Black on both terminations of the switch.

Depending on which electrical code was in-place at the time the original switch you may have Red, Black, White cable going to the switch. If that is true, look at the connection to the light fixture. If Red is connected to the feed of the light, then yiu will find Black feeding the switch, Red returning from the switch and Neutral either capped off or connected to the Neutral port on the switch if ot is required by the switch.

So, please tell us what is the wiring configuration of the switch.

I assume that this is a switch for lighting over vanity of a bathroom.

Describe wiring in the switch box.

You said,

Quote:

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Checked with voltage meter,

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Was that a multimeter or voltage sensor.

Here's a couple of scenarios:
Assuming you removed and replaced just 2 wires, when pulling on the switch (old) to remove it you separated an already loose connection.
A wire nut in the back of the box, a connection to another switch in the box etc.
Turn off the power to the circuit. Do you have a circuit tester? A non-contact type is advised for looking for the presence of electricity.
After making sure the circuit is off, pull the switch again and look around in the box. Look for loose wires, a wire nut that came off or any other evidence of an open circuit. Removing and replacing the switch would not cause the problem you describe but the actions taken to do so may have created another problem.
99% of most circuit failures are either incorrect wiring or open circuits.