MacBook Pro: Picture files show red rectangle/locked when opened to view image.

Seems to be an issue with Canon EOS R5 mark II .cr3. QuickLook might work with some .cr3 but might fail if the QuickLook view is scaled.

https://discussions.apple.com/thread/256241369

https://discussions.apple.com/thread/256248724

Use Adobe DNG converter until this is fixed. Or use Adobe Photoshop or Lightroom which seem to work.

https://helpx.adobe.com/camera-raw/using/adobe-dng-converter.html

I have no idea. I have not seen a "Locked" picture, and I can't see how to make one. By "open" you are meaning in the Preview app? How about Photos or Quicklook? I use Nikon's NEF files, and they continue to work just fine. Is this only new CR3 files, or is it the same with old files that you've seen open before?

It's interesting that the file, AirDropped to a phone, opens just fine. There might be some filtering in the AirDrop process. What happens if you AirDrop that same file back to the Mac?

Will the file open in Adobe's DNG converter app?

I would try restarting the computer (of course!) And I would try a restart in Safe Mode. This bypasses certain potentially disruptive processes, and it often helps. Safe Mode is different for different computers, so see this: 

Start up your Mac in safe mode - Apple Support 

In case it's a User account problem, I would make a new user and see if the same problem recurs with it.  I actually always keep an extra User account to try things in. Things like "Cleaner" apps, "Virus" apps, and VPNs can mess up a User account, for instance.

billbob_08 wrote: It’s just very annoying to have to open lightroom and import files just to see them.

Do they show in QuickLook-- select the picture and hit spacebar? Since you can do that with a bunch at a time, that's a great way to scan through pictures. Or start one, and "down key" through the rest of the folder.

It's disturbing that Preview doesn't work, though I use that mostly for PDFs. I use Photos as the main organizer of pictures.