MacOS Catalina – Second Screen Not Working

I know I am not the only person to have problems with the usbc – HDMI screen suddenly stop working and I thought I would never fix it today, but I have finally done it so thought I would share the technique – because it calls on a number of posts to resolve it.

Uninstall DisplayLink

First thing you need to do is uninstall the DisplayLink software extension that enables the USBC – HDMI link

  • open spotlight and search for DisplayLink Uninstaller
  • double click on the installer and follow the instructions to uninstall the driver
  • when you are prompted to restart your computer then do so

Reboot in Recovery Mode

  • as your system is coming back up hit <CMD> <R>

When the system comes up in recovery mode do the following

  • login as yourself

Mount your Hard Drive

  • open diskutility
  • mount your hard drive
  • close diskutility

Invalidate the Kernel Extension Cache

  • from the top menu select Utilities -> terminal
  • type in the following command
kextcache -i /Volumes/<your harddrive>

to find out your hard drive type

ls /Volumes

this will list your hard drive.

If the name of your hard drive contains spaces start typing the name of your hard drive before the spaces and then press tab

For example – if your hardrive is called Macintosh HD then type

kextcache -i /Volumes/Mac

and then press tab. The command line will complete the name for you (in this case it will display

kextcache -i /Volumes/Macintosh\ HD

Once the command has completed it will display a number on the command line.

Reboot as Normal



and let your computer come back up as normal

Install DisplayLink

Final Troubleshooting

When your computer restarts your second screen may still not appear. There are three checks to carry out:

1: Security and Privacy – DisplayLink Permissions

  • click on the Apple icon
  • open System Preferences -> Security and Privacy
  • click on the general tab

check that the DisplayLink app has not been prevented from running and if so click on the allow apps from DriverLink if it appears (not shown above)

2: DisplayLink Permissions to Record the Screen

check to see if the DisplayLink app has appeared in the Screen Recording window of the Privacy tab. If it is there then allow it to do screen recording

3: Manually start the DisplayLink app

Open a terminal window and type the following:

cd /Library/PrivilegedHelperTools/DisplayLink/


wait for a few minutes and your screen should come to life.

When it does, <ctrl> c in the command line and restart your computer



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