Hi hillstrom0036, first, just in case it's a transient permissions problem, could you do a normal shutdown of Windows 10 and start it back up again and see whether the installer works after that?

There also are "full" or "offline" installers available for cases where the small (stub) installer is hindered by your firewall or other security software. Those ca be downloaded on the following page (make sure to choose your preferred language):

https://www.mozilla.org/firefox/all/#product-desktop-release

Thank you. I was able to reinstall after a restart. I still don't know why it stopped working and understanding that might prevent issues in the future.

Unfortunately I was not able to recover any of my "Favorites" after reinstalling. I believe the data is still stored somewhere because I was able to import that data into Edge but not able to import from Edge back the new Firefox version. Is that data somewhere that I could get it back into the new Firefox?

Hmm, I don't know where Edge found the data. Do you have multiple profiles? Check the last section of this article: Recover lost or missing Bookmarks.

Alternately, Firefox might be able to import from Edge: Import Bookmarks and other data from Microsoft Edge.