1. Shut down the computer. 2. Unplug the computer's power cord. 3. Wait fifteen seconds. 4. Attach the computer's power cord. 5. Wait five seconds, then press the power button to turn on the computer. 6. Press and hold the Command-Option-P-R keys before the gray screen appears. 7. Hold the keys down until the computer restarts. 8. Release the keys.
Hello there if your still having issues you can disconnect the power cord. Then with the power cord disconnected hold the power button for 60 seconds. Then reconnect the power cord and attempt to turn on your mac.