The most common problem with MySQL Server not starting is another mysql service running on the same port. To check this
- Quit MAMP PRO.
- Open the Activity Monitor located in your /Applications/Utilities folder.
- Type "mysqld" into the search field on the top right.
- Quit every process you find after your search.
- Restart MAMP PRO.
If MySQL still refuses to start check the log file for error messages.
If you see this error, or a similar error with your mysql.user table
2018-09-06T14:39:07.778314Z 0 [ERROR] Fatal error: mysql.user table is damaged. Please run mysql_upgrade.
2018-09-06T14:39:07.778359Z 0 [ERROR] Fatal error: Failed to initialize ACL/grant/time zones structures or failed to remove temporary table files.
2018-09-06T14:39:07.778614Z 0 [ERROR] Aborting
Do the following ...
You can't run a MySQL database upgrade because your MySQL server does not start in the first place, you could try to add the line "skip-grant-tables" to your MySQL configuration file at the end of the section "[mysqld]" and then try to restart the MySQL server. This will tell the server to ignore your defective users table during startup so it can be upgraded afterwards.
To add this in MAMP PRO, open your MySQL template file. Go to File > Edit Template > MySQL > my.cnf
Now start your servers.
The server should start and you should be able to perform a database upgrade via the MAMP PRO main menu "Tools > Upgrade MySQL Databases".
Don't forget to remove the added line afterwards and restart your MySQL Server.