ERROR! MySQL manager or server PID file could not be found! QNAP

I tried everything above, but saw no results until I got a hint from here: https://superuser.com/questions/159486/how-to-kill-process-in-mac-os-x-and-not-have-it-restart-on-its-own

I eventually went over to the activity monitor in my Mac, force Quit the PID, and ran the command:

sudo /usr/local/mysql/support-files/mysql.server restart

The magic was done!!!

After a lot of searching, I was able to fix the "PID file cannot be found" issue on my machine. I'm on OS X 10.9.3 and installed mysql via Homebrew.

First, I found my PID file here:

/usr/local/var/mysql/{username}.pid

Next, I located my my.cnf file here:

/usr/local/Cellar/mysql/5.6.19/my.cnf

Finally, I added this line to the bottom of my.cnf:

pid-file = /usr/local/var/mysql/{username}.pid

Hopefully this works for someone else, and saves you a headache! Don't forget to replace {username} with your machine's name (jeffs-air-2 in my case).