Address already in use - bind(2) for "::1" port 3000 (Errno::EADDRINUSE

You need to kill the puma process first ; Run this command in the terminal   lsof -I :3000  to show what is using port 3000   

Now run the following to kills the instances/process.  kill -9 59780. ;(where 59780 is the PID using my port)