Wont take a jump 1996 6cyl jeep grand cherokee laredo

I would buy new battery to make sure you have the proper 12 volt current at least , but need more info on the your jeep.

Get a hammer and punch. Tap on punch next to key while turning key. This will free up frozen tumblers in ignition

Check to see if the fuel pump is running after it shuts down...could be a relay or the pump itself (overheating internally) Checked the fuel filter yet? Some crank sensors need to be shimmed. If it's too close to the flywheel even though you recently changed it, if it's too close to the wheel it can fail again. May not be the case but worth checking over. Also check the ceramic resistor on the left fender near the master cylinder if you have one. That too can cause problems.

clean battery terminals and recharge battery we will go from here hear from you soon Lee Davidian

Next time you replace your battery you need to find one with more cold cranking amps. It is much harder for the battery to produce the voltage needed in the cold. Batteries produce their peak amperage when new which may explain why you have no problems for a year.

Have the alternator and the battery tested as one if not both items may have gone bad.

take off your distributor cap and turn the engine over, does the rotor spin around? if not might be your timing belt! and if it does spin it still could have jumped a tooth on your timing belt? can you poor a little gas down the carb ? will it try to start? if it does but backfires then your timing belt may have jumped a gear or two...

I have a 95 Grand Cherokee, its got this built-in 'kill switch' (lol) that i had to figure out - the alarm wouldn't stop going off until i put the key in the driver door, then turned it Right-Left-Right...

Your probably already aware of this nuisance, but i thought i'd post it it just in case.

You probably blew a fuse.
Look under the hood for the fuse box and check the BIG fuses.

it might be ur header