I just had a version upgrade of Firefox and I can no longer access my bookmarks and other information.
Firefox upgraded its version and when I launched Firefox it required me to create a new profile. I have since followed the instructions to attempt to restore the previous profile but it will not allow me to replace the new profile with the old profile. Under the new profile, I can not access my old bookmarks, history, ... I have followed the articles but this is not addressed. Can you provide me with more detailed instructions how to migrate a previous profile into the existing environment without receiving the following pop window entitled: You've launched an older version of Firefox with the following message - Using an older version of Firefox can corrupt bookmarks and browsing history already saved to an existing Firefox profile. To protect your information, create a new profile for this installation of Firefox."
You posted with a Firefox 91.10.0 ESR user agent while the current release is Firefox 101.0.1. The Firefox ESR releases are aimed at enterprises where updating every four weeks to a new major release is too much work with testing for issues (ESR only receives security updates). . I'm not sure how you got end up with this ESR version since the message suggests that you previously used a release version or at least a version newer as 91 ESR. You can download the current 101.0.1 release and uninstall the 91 ESR version. The release version should give you access to the old profile.
You can find the full installer of the current Firefox release (101.0.1) in all languages and all operating systems here: