The updating, whether done "automatically" through wifi or manually with a usb drive, seems to be a weak point of Sync 3. Many problems are reported, and it often doesn't work. I'm still on V 1.0. It started to auto-update last May, showed a progress bar that went up to about 40% complete, and never went any farther. If I wanted Android Auto I'd be very frustrated at this point, but I don't because I don't plug my phone in, I just let it Bluetooth. Ford told me it would work better if I had a stronger wifi signal in my garage (I usually have 2 bars there), but that to me is itself a weakness in the system- most people are not going to have a super-strong wifi signal outside their house where they park. I'm parked in an attached garage about 35' from my router. I once tried pulling into the yard right outside the wall from the router-no difference.
So I've decided not to worry about it, I'm not patient or persistent enough to keep pursuing this particular issue.