Key Not Recognized

The Immobilizer System indicator light comes on for a few seconds, then it goes out when you turn the ignition switch to the "On (II)" position. The Immobilizer System light will blink if it cannot recognize the key coding. This can happen if you have the correctly coded key but you also have other immobilizer keys on the same key ring or a metal key fob, or if metals from other keys get in the way while you try to start the engine. Use a key fob made of leather or plastic, and keep other keys away from the ignition and your master or valet key while starting your Honda.

I'm not sure with Honda but I do know with Porsche vehicles with immobilizer, if the car would not start and the immobilizer light stayed on ("Immobilizer Active"), generally the key head needed to be recoded (if you still had the code number for the original key head) or a replacement key head (that comes with new code number) needed to be used. To do this you needed Porsche's computer hooked to it. Now days, Porsche's need to be connected directly to Porsche's website to code new keys. I can't imagine Honda would make it so convoluted but all manufacturers are heading that way. Obviously you've already tried disconnecting and reconnecting the battery terminals.
Thanks