salvage head unit, sync not right

[Dandan 0]

A few days ago, my wife's 2013 Focus SE radio (standard 4-speaker CD player) started playing static loudly and wouldn't shut off. I had to pull the fuse to quiet things down. Earlier today I went to a local junk yard and pulled the head unit from a 2012 Focus (compatible, supposedly) and installed it in my wife's car. The box looked and connected identically to what I removed. When I reinstalled the fuse and turned it on, all seemed well. The radio played and the Sync menus appeared. The phone paired and the contacts downloaded, but that was the end of it. There are no voice prompts coming from the system now. Activating the system with the steering wheel control brings up the animated icon on the screen and the voice command message, but no sound comes from the system and there is no response from the system when it's given a voice command. I found the prompt command in the menu and made sure it's on, and I did a full system reset as well. Is there anything else I should do? Is it possible that there's a difference in compatibility between a '12 and '13 radio/Sync system?