Will not awaken from sleep if cover is closed

First, I would Restore Defaults in Energy Saver preferences, here is how:

1. Choose System Preferences from the Apple () menu.
2. Click the Energy Saver icon in the System Preferences window.
3. Click the Restore Defaults button in the Energy Saver window.
4. If you are on a Mac notebook computer, click the Battery or Power Adapter tab to switch settings. Click the Restore Defaults button in both panes if needed.

Source: https://support.apple.com/en-us/HT204760

Second, make sue the following is taken care of:

1. Make sure the computer's battery is charged. Try connecting the power adapter to the computer, then press the power button for one second to see if the computer powers on.
2. Make sure the AC power cord is connected securely to the power outlet, and that the outlet it is working correctly. Confirm the power adapter or cable is attached firmly.
3. If your computer is plugged into a power strip, make sure the power strip is not turned off. Check to make sure other items connected to the power strip are receiving power.
4. Confirm the right power adapter is connected on Mac notebook computers. If a lower wattage power adapter is used than the one that came with your Mac, it may not provide enough power to charge the battery while the computer is powered on. Make sure there is no debris in the MagSafe port that might prevent charging. When your MagSafe cable is connected properly, you should see a green or orange light on the connector.

Source: https://support.apple.com/en-us/HT204760

If you're still having issues, you may want to reset the a SMC and reset NVRAM/PRAM.

• For NVRAM/PRAM: http://support.apple.com/kb/HT1379
• For the SMC: http://support.apple.com/kb/HT3964