Icon of the PDF file does not display as a preview

Hello, I just started using DEVONthink and I would like to ask a silly little question.

Since yesterday, the icons of my new added PDF files only show the blank, instead of the preview image. I don’t know if I’m making myself clear, I’m just trying to say that the icon of a PDF file should normally be the preview image of the first page, right? But now it doesn’t display anymore. And I need to emphasize that those affected PDF files themselves can be read normally.

Is there a problem with my settings? What can I do to make the icon of the PDF file show as a preview again instead of a blank? Thank you in advance.

Welcome @lelool

Do you have Preferences > Files > Thumbnails > PDF & Postscript Documents enabled?

Also, you can add a thumbnail as needed. Select a document without a thumbnail and choose Data > Thumbnails > Create.