I'm having this same problem. It can't find the zone. Does anyone know what I could be doing wrong?
I don't know if this will help you, but when I was trying to select FedEx, it was initially acting funky, going to an "Install" button instead of the Choose 0 or 1 and Handling Fee right pane. I just had to click around in other options and click back on the FedEx one until it worked. I also, changed it from 0 to 1 a couple times and it helped.
Now my problem isn't that it's not selected, but that it can't read the zones properly.