I recently replaced my 3 light fixtures on my ceiling that hold 3 light bulbs each .then replaced them with 2 three bulb track lights,and capped all the wires on the 1 remaining .after I completed this I turned on the lights and they worked! Then I tried to install a dimmer switch and nothing now works. I have since gotten rid of the dimmer switch and just tried to relace the switch with a similar switch and they still do not work . Any Ideas on what I am doing wrong. Thank you

Bypassing dimmer/switch is a good first, then while you're their, you could check for voltage.
Could be a wire at track.
After it works with a switch, then install the dimmer.