Note that Firefox 100.0 is about to be released next Tuesday, so updating now to Firefox 99.0.1 is rather late.

Version 99.0.1, first offered to Release channel users on April 12, 2022

• https://www.mozilla.org/en-US/firefox/99.0.1/releasenotes/

See:

• https://support.mozilla.org/en-US/kb/recover-user-data-missing-after-firefox-update

Sometimes when the browser thinks there is a problem with the profile, it will create a new one.

Look on your desktop. Do you see a folder called; Old Firefox? Look inside. Look for the folder with the latest creation date.

https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile

https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles

https://support.mozilla.org/en-US/kb/how-run-firefox-when-profile-missing-inaccessible

https://support.mozilla.org/en-US/kb/recover-user-data-missing-after-firefox-update

Thank you all for the assistance. Problem solved. Incidentally, when I upgrade to 100, if I have a problem with it, will the standby profile revert to the problematic 99.0.1 or the reloaded profile I used to clear the 99.0.1 issue.