My truck won't start

What testing have you done? Make sure battery has a full charge and battery cables connections all good? If it cranks good but won't start, have a helper crank it while you visually check for spark at the plugs. Use a gage and check proper fuel pressure and fuel injector pulse? Any applicable trouble codes? Now if your missing ever thing to do with fuel and spark, have to check rpm signal. Some dodge vehicles, the computer has to see both the cam and crank sensor signals or the vehicle won't start. I haven't checked your security system? just a thought.