Suddenly can only manually mount disk images from Disk Utility I used to be able to mount disk images from the Finder via ⌘O, Double clicking, etc. but after using High Sierra for 1 day, it suddenly couldn't anymore in the middle of me using it.

Can anyone help? I can't think of any reason this would have happened.

I can still mount disk images, but, as explained in the title, I need to do it manually from Disk Utility.
Restarting Mac OS fixed the problem.