You mentioned that you used both a Mac and Windows PC to create the USB drive. Some users have had issues with using a Mac in properly setting up the USB, so just be sure you have it correct. I’m guessing it was correct since you got the same error for both of them.
Here’s what I would try based on what you have already done:
First, I would disconnect the battery for a short time (5-15 minutes) to let all the hardware power down and reset. Reconnect the battery and let everything come back up and then try the update again. Be sure to READ your owners manual about things to check when the 12v battery is changed or disconnected as you may need to reset some functions in the vehicle.
If that does not solve the problem, then I would try a Master Reset if you have not already done so. This will wipe out all your personal settings (phones, Nav favorites, etc.) and reset the system to factory options using whatever version is currently installed. Then try the update again.
If none of the above works, then a dealer visit may be necessary. Many users have tried an alternative update process provided by Cyan Labs. This is not a Ford supported procedure so it comes with some risk. However, many have used it with no issue. I have not used Cyan Labs myself.