Here’s a fairly simple solution that can take care of a bunch of different problems on your Mac. If your Mac is acting quirky, resetting the SMC might just help clear its brain. How you do it depends on which model of Mac you’re using.
If you have an older Apple laptop with a removable battery, you need to unplug the power supply and remove the battery. Then hold down the power button for about seven seconds. Now, put the battery back in and start your laptop up again.
You may need an extra hand to assist with a newer laptop that has a non-removable battery. Plug in the power supply, then press and hold Shift + Option + Control and press the Power button. Hold all of these keys down at the same time for seven seconds. Then release all of them at the same time.
For desktop systems, shut the Mac down. Then unplug the power cord. Wait 20 seconds before plugging it back in, then another 5 seconds before turning it on.