Try restarting your Mac.
Try Safe Boot:
- Shut down your Mac
- Wait until your computer turns off and after that press the Power button
- Right after you hear the startup tone, press and hold the Shift key
- Release the Shift key when you see a grey Apple sign and the progress bar below this sign
- After your Mac boots up, restart it as you usually do.
If this doesn't help, follow the instructions below:
- Shut down your Mac
- Wait until your computer turns off and after that press the Power button
- Right after you hear the startup tone, press and hold the Shift key
- Release the Shift key when you see a grey Apple sign and the progress bar below this sign
- Once you see Desktop, start a Disk Utility scan to detect and repair file system errors (don't forget to choose your main hard drive)
- Click on Verify Disk and then, if asked to fix problems, on Repair Disk
- After this, click on Verify Disk Permissions and then on Repair Disk Permissions
- After the process is finished, shut down your Mac and turn it back on after about 30 seconds
Apart from that, take a look at this Apple article and follow the instructions on Resetting NVRAM shown there: How to Reset NVRAM on your Mac - Apple Support
Try resetting the System Management Controller: https://support.apple.com/en-us/HT201295
