I have no idea how this registration thing can be solved, but I know that the latest firmware is NOT A GOOD THING for the RM/RML mixers. The beta version was released as final version, with all the bugs in it. It neither brought improvements, nor added new features. The firmware update was only good and needed for the CS18AI. The combination of "old" (RM32AI) and "new" (CS18AI) works perfect. The Firewire Display Lag was anyway not solved. And do not count for any futher update, because the RM mixers are legacy products.
Try to get the former firmware back to your RM. Maybe this also solves your registration problem.