I've got a Behringer LC2412 that won't illuminate my pars using DP 415 dimmers

Are your dimmers set to DMX mode or are they running internal programs? I bet that's not the issue.

The LC2412 is only a 24-channel lighting mixer. Are you setting your DP-415's to the correct DMX channels? I bet that is your problem right there, your DMX assignments are not correct.

Of course, the typical: is it turned on, is DMX connected? Is there a DMX signal indicator light and if so is it blinking(there is a DMX indicating LED and it should be blinking).

Are you sure you're not in blackout mode? Blackout over-rides everything, regardless of fader settings. Do you have your channel assignments on your controller done right?

Are your bulbs burned out? Are the fixtures plugged in?

Sorry, I'm shooting from every angle. You didn't provide a lot to go off of.

Start simple: is everything powered up. Check DMX channel assignments via the DIPS on the DP-415. Good bulbs? DId you change DIP switch settings? If so, power cycle(remove power, re-connect to power). DMX running? Using DMX cabling(prefered). DMX LED blinking?
Console assignments done properly?

You want to see at least the LED channel indicators light if you don't want to plug in fixtures. If you're getting this far, you're good.