For the past couple of months, I’ve had this issue with my MacBook. The background on the lock screen went gray and I tried all I could to fix it. It shows the regular blurred background image after a fresh reboot, but immediately the system auto-locks, the wallpaper on the lock screen disappears and all that’s left is this gray background:
I tried several fixes suggested in forums that didn’t quite work.
Contents
Setting a custom wallpaper
One of the fixes I read suggested using a custom wallpaper. I was using the default High Sierra wallpaper when this happened and tried using a custom wallpaper from my images. Well, I restarted the MacBook and the new wallpaper was displayed at login. Immediately auto-lock was activated, the problem came back. This didn’t fix the issue as I still had a gray lock screen.
Checking if com.apple.desktop.admin.png was present
Another fix suggested I check Macintosh HD/Library/Caches for an image file named com.apple.desktop.admin.png. It was present and this image is actually the blurred version of the current wallpaper. Using a custom com.apple.desktop.admin.png image still didn’t fix the problem.
Updating to the latest version of High Sierra
Thinking it was a bug with my version of macOS, I updated to the latest version (High Sierra 10.13.3). This still didn’t fix it.
Reduced Transparency: the real issue
This problem looked like something I actually caused. I only had to uncheck “Reduce transparency” from the Preferences.
– Go to System Preferences > Accessibility > Display.
– Make sure you uncheck ReducedTransparency.
– Restart the computer and everything should work fine. This is exactly how I was able to fix the gray background on the lock screen.
Note: Some apps like Duet automatically mess with your transparency settings.
If the ReducedTransparency option keeps getting marked after every restart, you need to disable it from such apps.
Thank you so much. This actually worked.