Change out radio now it won't start. both radio's are after marke

Check your switch that runs to your aternator.make sure is grounded .if not get a sand paper and sand it down.also check the switch that plugs in to the alternator.

It's a Mercedes, so electrical issues are extremely common. The ML especially of that year is about the most problematic car Mercedes ever produced.
It has issues everywhere from short circuits due to the wiring shrouding breaking down over time, to ECMs/ECUs failing without necessarily any good reason to. As there are too many faults on that particular vehicle to mention, it won't be easy to diagnose this one over the internet. You will likely require an auto electrician, and perhaps not even just one workshop to manage all types of issues. My best advice once you've dealt with this one and the vehicle is working is to sell it. You won't stop working on expensive issues with this mark and model.

The click you are hearing is most likely the start slenoid making contact, however you should short the large wires @ the solenoid to make certain the starter still doesn't run, if so try tapping the starter with a hammer to shift the comutator a litle and try to start. Even if it now starts the starter will continue to give you problems so the proper fix is change the starter

Are you saying the engine cranks but won't start, or the engine won't crank ?
If the engine does not crank, you would check for voltage at the starter, the neutral safety switch, and the key switch as well as the ground connections.

It is in Theft lock from the loss of power. Contact your local dealer for help getting it unlocked.

battery dead.

you now need to check for 12 volt power, and signal to the coil, also be sure all you timing marks are correct, if you have no spark, unplug one of the injectors and using an led test light check for injector pulse power across the two terninals while cranking, if you have no injector pulse then you could have a problem with the ignition passlock system, or key decoder

electronic key on 2008 jeep cherokee says key damaged or key not programmed. car won't start. some things work but radio won't come on. etc..

immobilsor has come on so only course of action is to call a specialist auto locksmith or the dealer to release the immobilisor ,have you lost the chip out of the key?? have a look and try the spare key

the code should be in either that car user manual or radio user manual.

radio codes normally work as follows :

to change the first digit you press button marked "1". to change the second digit on the LED display press button marked "2" and so forth