Hi Sidney and Welcome. My Name is ***** ***** I look forward to assisting you today with your question.
It looks like we're dealing with an hardware issue probably with the internal board. The reset you've been trying is called SMC (System Management Controller) Reset which is supposed to fix the sleep issues permanently. Even if the Mac is unable to wake up from Sleep, it should have reponded when you hold down the Power button for 5-10 seconds. To make sure this is not a glitch with the hardware or software, we can do some troubleshooting.
First reset the System Management Controller of your Mac. Follow the steps below;
Shut down the computer.
Unplug the power cord and also disconnect all other devices.
Wait 20 seconds. Hold down Power button for 5 seconds.
Attach the power cord.
Wait five seconds, then press the power button to turn on the computer.
This will reset the SMC. Now I want you to reset the PRAM and NVRAM of your Mac. Follow the steps below;
Shut down your Mac
Restart and immediately hold down Command-Option-P-R keys at the same time
Hold the keys down until the computer restarts and you hear the startup sound for two or three times.
Release the keys and let the Mac boot up.
Then turn off your Mac. Then turn it back on and immediately hold down Command and R keys at same time for 20 seconds and this will boot your Mac to the Mac OS X Utilities screen. From there, click Disk Utility. Select your hard disk at left column (Macintosh HD or hard disk name). Then click First Aid button and run it. Repair if asked.
Please let me know if that didn't work, so we can continue troubleshooting
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