I have a funny glitch. I am trying to set Photoshop CC as the default app to open all PSD files on my Mac. I am setting it the proper way (through the Get Info window in the Finder, Change All, then clicking on the Continue radio button), but each time it defaults back to Photoshop CS5. If I choose another app as a test (any that shows up in the drop down window, e.g After Effects CC, Illus. CC, whatever), the "change all" selections sticks, but not with Photoshop CC. Any ideas?
Try running Disk Utility's First Aid on the drive to fix permissions. Not positive but that would be the first thing I would try. I assume you are logged in with Read and Write permissions (visible in Get Info) since you were able to make the change with other apps, so the change should stick.
Sorry for the trouble setting Photoshop as the default application for PSDs on macOS. This is a known issue that we're working on currently. Please add your vote and voice to this thread to be notified of any update/fix: Photoshop CC 2018: Not default program for PSD files (macOS) | Photoshop Family Customer Community