When I start my truck, I get the following SYNC notification pop-up. These seems to only have happened recently. It should be connecting to my home wifi since its one of the added networks.

 

Hi, welcome to FTE, I'm afraid I personally don't have an answer to your question, I did however come across a post in another thread that might be something worth considering, it reads as follows:

I have never been successful updating my Sync via WiFi. My home internet is too slow. I did the USB update from the Ford Owners website. When I logged on, it said there was a new update to my Sync, I downloaded it to the USB thumb drive, and stuck it in the USB slot in the console and it worked fine.

I have had the popup message before also. Once I connected to my home WiFi, the message went away. Also, you can turn off Automatic Updates in the Sync Settings and it disables the popup message.