Sometimes when you start MAMP, the mysql server refuses to start up.
Solution 1
Sometimes this is because it is already running from a previous session. To fix that, quit MAMP, open up Terminal and run the following command:
killall -9 mysqld
Then restart MAMP.
Solution 2
If that doesn’t work, here’s another fix that has worked for me on occasion. Quit MAMP, then navigate to
/Applications/MAMP/db/mysql56.
Note: the number at the end of this file path may be slightly different, depending on which version of MAMP you use.
You can navigate in the Finder or in Terminal.
From that folder, delete the last log file: look for a file called ib_logfileN (where N is the higher number).
Then restart MAMP, of course.