When you upgrade MAMP, it will preserve the existing installation to a folder that is called MAMP_current-date, something like MAMP_2022-04-14_08-00-00 (the last bit is a time stamp). You can revert to the previous version by renaming the current MAMP folder (under the Applications folder) or delete it, then rename the previous version with the date and time stamp appended to just MAMP. Then restart the MAMP services to see if you can access your WP site.
