I had this same problem with MusicFab and an error from Amazon about having to update my browser…
But I’m running two different machines with MusicFab, and one continued to work, and one didn’t. I’m not a software person, so I don’t know exactly what’s going on–or how MF uses an “embedded” browser or whatever, but since one worked and the other didn’t, I concluded that it must not be an issue with having to get a browser update through MF update–but maybe just updating my browsers on my computers…?
Anyway, I updated MS Edge on the non-working computer, and lo and behold, MF for Amazon started working again! {Edge is set as my default browser at the moment}.