Quick Links and how to for resetting NVRAM/PRAM and SMC
How to reset NVRAM or PRAM on your Machttps://support.apple.com/en-us/ht204063
Power on, quickly hold Option + Command + P + R, wait for startup sound, release.
How to reset the System Management Controller (SMC) on your Mac
for Mac Notebooks:
Shift + Control + Option then Power button, hold 10 sec. then release, Power back on.