Problem with my navigation disc

I have a 2006 Prius with a Gen 5 navigation unit. My current nav disc contains 8.1 data and it works fairly well. I just received a new nav disc with 12.1 data. My nav system barely reads the new disc. I can't enter any addresses or display maps. More importatly, I can't change the zone to 10 for Florida. Nothing works.

I checked with my dealer and they couldn't help me. They don't know anything about the nav system. If a customer comes in with a failing nav system, they obtain a rebuilt system and do a swap out. They have no idea why my system couldn't read the 12.1 disc. The parts manager did verify that the disc is the same series as the 8.1 disc and he thought the 12.1 disc should be compatible.

Does anyone have any ideas on why I can't use the updated 12.1 disc?