The Preview app will no longer open jpeg and pdf files

Shutdown your iMac. As soon as you press the power button, press and hold the shift key to boot into Safe Boot Mode. You will see confirmation of that in red letters in the upper right of the screen as you reach the login screen.

In the Finder, select your home directory > Library. In that Library folder, locate and double-click on the Caches folder. Press cmd+A to select everything in that Caches folder and then press right-click and choose Move to Trash. Do not attempt to empty the Trash. Quit the Finder window and reboot normally.

On the reboot, empty the Trash and try opening any jpeg or PDF file in Preview. Any change?

Don't worry about what you removed from the Caches folder as it will get rewritten as System and user processes access it again.

nextdoor wrote:

Hi VikingOSX, you're to something!

I copied a PDF file and a JPEG file that was in my One Drive, which could not be opened by Preview, on to iCloud Drive, and they still could not be opened. I then created a new JPEG file and new PDF file that had never been on One Drive, onto my iCloud Drive and voila, both of them could be opened. So One Drive does interfere with this.

But it doesn't explain why my other Macs can handle opening these files from One Drive.

Perhaps on the other Macs, you used the OneDrive application to retrieve the files from OneDrive, decrypting them in the process as written to the Apple filesystem.

Hi VikingOSX, you're to something!

I copied a PDF file and a JPEG file that was in my One Drive, which could not be opened by Preview, on to iCloud Drive, and they still could not be opened. I then created a new JPEG file and new PDF file that had never been on One Drive, onto my iCloud Drive and voila, both of them could be opened. So One Drive does interfere with this.

But it doesn't explain why my other Macs can handle opening these files from One Drive.

We have the same iMac, though mine has 40GB of RAM. Mine is running Monterey 12.7.6 and has no issues with performing a Safe boot as I described earlier. I see no issue in your EtreCheck report that would interfere with a normal Safe boot process.

Are you attempting to open images and PDFs directly from Microsoft OneDrive with Apple's Preview? It is my understanding that OneDrive encrypts anything copied to it and only the OneDrive application can reverse that encryption for normal file access on macOS. Could this be the Preview issue? I too have current Office 2021 applications but chose not to use OneDrive and excluded it during installation or for use by the MS applications.

Thanks VikingOSX. Unfortunately I can't seem to use Safe Mode. I've explained why in this thread Mac OS Sonoma 14.6.1 download stops partw… - Apple Community

I've tried doing Safe Mode again and it doesn't allow me to do anything other than quit and reboot. I've tried moving the Caches to Trash in normal mode but that doesn't work, sadly.

Where possible, keep the OneDrive application version current wherever you are using it. As I mentioned earlier, I have Office 2021 Home and Business installed but opted to not install or use the OneDrive application or service to keep things simple and keep my Office documents on Apple filesystems. That decision prevents me from sharing your current circumstances.

On all my Macs, I use the One Drive application to work with my files, so it shouldn't be different on any of them. But I will ponder if I'm doing anything different without being aware of it.