My 2014 Cherokee suddenly will not start. What could be wrong?

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 visuall check for spark at the plus. If spark everywhere, use a gage and check proper fuel pressure. Check fuel injector pulse. Any applicable trouble codes? Those are the basic checks in my opinion. You have to test when problem is ongoing. If your missing everything, spark==fuel==whatever, I'd have to check for rpm signal. Check cam and crankshaft position sensors and wiring circuits. I'm not saying replace anything, but, you need to do some testing.