Here is what you can do. That helped me once.
You need to get to mainboard and find there flash memory. In my case it was chip - 25Q64BVFIG. It contains firmware for that machine.
Then - need to desolder it, reprogram using programmer with support of that type of schemes and solder it to mainboard again.
Downbelow will be a link for dump to download (must mind you - that Canon iR-2420 was in Russia and I'm not sure about differences between US/Canada and European firmwares. Just to let you know that beforehand - that there might be some problems to show up. But I suppose - since machine will finish loading inner software and comes to ready state - you can just figure it out by playing with local/country settings). These are photos before and after (connector melts a little)
- About dump - it's ready to use with your programmer - it's been taken from newly installed machine (not by me - but from guys from similar Russian tech forum). DUMP for reflash memory chip
- About programmer - mine is - TL866A - pretty simple and cheap
Good luck! Hope that will works for you!