Time to get the volt meter out and find out what is missing here. Again, a high speed fan indicated the FCM is powered up, but it is not getting its 'tickle' pulses from the ECU.

WHY NOT?

And the starter won't engage.

WHY NOT?

BOTH of these indications point to an ECU that is not 'running', that is, is not powered up. If you look in the wiring diagram of the service manual, go to "power distribution" and look for all the 12 volt inputs to the ECU. I'd bet you MONEY that at least one of those inputs is dead, that is, not at 12 volts or so, but at essentially zero volts.

If your RCM is used, it's probably bad. If your RCM is actually NEW, you must figure out why you are getting symptoms of no "engine control relay output" from the RCM to ECU.