Can no longer edit catalogue from Smart Previews

[yolandap49255734]

Hoping someone can help, please. I edit photos made available as smart preview catalogue by photo owner in Dropbox.

Have previously been able to simply open catalogue, edit and export back catalogue to Dropbox so the photos sync at other end.

Now, when I open a catalogue in Lightroom Classic from Dropbox, I get grey photos with an error saying can't find photos. Eg:

“NCSP2048.CR2” could not be used because the original file could not be found. Would you like to locate it?

[F. McLion]

Are you sure that Smart Previews have been generated before starting your copy process?

What does it say just below the Histogram if you select a photo in question? Is Smart Preview shown?

[Mariam Hovhannesyan]

Can it be a problem with Dropbox? Did you try to download it and open from desktop not from dropbox?

[JohanElzenga]

Dropbox has an 'online only' option, where the local file is just a link. Make sure you have not enabled this, because Lightroom cannot work with that.

Another possibility is that you need to give Lightroom 'full disk access' permissions. See https://community.adobe.com/t5/lightroom-classic-discussions/quick-tips-how-to-give-full-disk-access...