You can revert back to MAMP PRO 4.5 by downloading it here
https://www.mamp.info/en/downloads/older-versions/
Note: Please make a backup of /Library/Application Support/appsolute/MAMP PRO/db folder and your host files as well before proceeding.
- Remove your /Applications/MAMP PRO.app application.
- Install MAMP PRO 4.5 over your current installation of MAMP PRO 5.xx. DO NOT use the uninstaller in your MAMP PRO menu, this will delete your database data.
- Rename your /Library/Application Support/appsolute/MAMP PRO/db/mysql56_2018-XX-XX folder to /Library/Application Support/appsolute/MAMP PRO/db/mysql56
- Rename (or remove) your /Library/Application Support/appsolute/MAMP PRO/db/mysql57 folder. This is your MySQL 5.7 upgraded data which is to be used in MAMP PRO 5.
Your MAMP PRO 4 (MySQL 5.6 data) can be found in /Library/Application Support/appsolute/MAMP PRO/db/mysql56 - Delete the file: Users/username/Library/Preferences/de.appsolute.mamppro.plist
Note: If you open MAMP PRO 4 again, and receive a warning, specifying a mismatched MAMP.app, then re install MAMP/MAMP PRO 4 again (the installer did not install a matching MAMP.app in /Applications/MAMP, which is causing the problem). When the installation is done, you should be able to start MAMP PRO 4 and start your servers.