My rather interesting saga on this update ...
When I went to the map website and entered my 2020 ST's VIN, it offered me another "free" update. I was happily surprised as I only expected one such update (which I had used a year ago for the NA 2.20 version). I downloaded the files, including a license file, and ran the installer. Eventually it failed by simply exiting, and the NA 2.20 remained on the "About" screen.
I sent an email to the vendor, and got back a reply to contact Ford (hmmmm ... right there I knew this would be a difficult, as clearly this was a problem with the download files ... not my Sync unit), but I humored them. I called Ford and, sure enough, after a few Q & A's about my system and a soft reset, I was referred back to the vendor. The Ford rep did confirm that there had been a couple of reports from others about the "free" update, including one Lincoln owner who had the same problem as I did as well. I sent another email to the map vendor ... and still have not heard back.
But ... in the interim, I re-downloaded the full update (using my M1 MacBook Pro), and tried again yesterday. After at least one restart, it finished perfectly, told me to remove the USB and the install would finish after a key cycle/power cycle. Sure enough .. now on NA 2.21.
My guess ... there was something amiss with the website that gave me a "free" update, and the initial set of files were not configured correctly somewhere. The second set (about a week later) had been corrected and thus worked OK. I'm geeky, but not enough to see any difference in the files ... they all look identical right down to the names, dates and sizes. But, second time around worked, so all's well!!
Ken