Are you looking for the solution of DebugKit Toolbar not visible in CakePHP 3? These small tips will help you do that. Ensure you have pdo-sqlite installed & enabled on your machine. Cause debugKit by default uses a sqlite db. If not then follow this instruction.
At first install pdo-sqlite in your machine.
sudo apt-get install php7.0-sqlite
Then restart your server (apache server)
sudo service apache2 restart
Now that will help you to visible the DebugKit Toolbar