OK if you replaced the ignition switch you would have noticed if the Actuator Pin Assembly that turns the ignition switch had broken off...a common problem.....if this actuator pin is starting to break then ignition lights come ON but engine will not turn over...turning the ignition switch with a small flat screwdriver while ignition key is in its normal slot will turn over the engine.
The red LED on the LHS of the cluster is part of the SKIS anti-theft system.
The chipped ignition key has its imbedded code read by the SKIM module that sits on top of the steering column and has a wire loop going around the inserted key. The SKIM module reads the chipped code and sends it to the ECM inside the engine bay.
If the ECM is happy with the code received it turns off the red LED, energizes the ASD relay and allows the engine to turn over and fire.
If the ECM is not happy with the code received it will flash the red LED permanently but allow the Jeep to turn over and fire but will cut out after a few seconds.
If the ECM was happy with the code but did not receive confirmation back from the ASD relay that it...the relay....had energized then the red LED stays on all the time....engine will turn over but never fire.
So the first thing to do is to is to try a different ignition key and swap over the ASD relay in the box under the hood with an identical one next to it. I had this problem on my 2002 Export CRD due to the ASD relay not energising due to a broken wire going to the relay coil...I removed the ASD relay and jumpered female pins 30 and 87 together inside the empty socket. This turned the light off and enabled me to start the Jeep and drive it until I had time to fix the problem.
There is a known problem with the LHD 2006 CRDs that the main harness goes behind the Fuel Filer Head Mounting Bracket and can get damaged in that area and cause shorts down to chassis.
So unplug the battery, remove this fuel mounting bracket and check the wiring in that area for damage. Also re-plug the connectors on the ECM a few times to clean up any bad contacts and swap over the ASD Relay.