Can not Delete the grey files

[PleinCouleur]

Dear people, I have tried to delete the gray files but when I click delete, Lightroom does not respond and I do not get a notification? Who can help me. 

{Moved from Lightroom Cloud to Lightroom Classic Forum by Moderator}

[Rob_Cullen]

Lightroom-CLASSIC error!

An answer (well worth a try!!)  given by John Ellis at the link shown below can be summarized as-

1) Go to the 'All Photographs' option in the Catalog panel to show ALL photos in Grid View.

2) Un-stack all stacks. MENU: Photo > Stacking > Expand all Stacks

3) Select ALL photos EXCEPT for the Grey problematic thumbnails.

{Hint: First select the Grey thumbnails, THEN invert the Selection! MENU: Edit > Invert Selection}

4)  Export as a new Catalog.  MENU: File >Export as Catalog

5) Continue using the 'new' catalog.

GHOST ZOMBIE IMAGE ANSWER John Ellis

Are you upgraded to v10.2?