Using the latest eM Client for Mac V10.1.4411 using Sequoia 15.0.1, when i receive a new email with a .pdf attachment using eg: a Gmail IMAP account, if i then hover over the attachment the little dotted line goes across the top of the preview window for a few seconds ok, but then once the small dotted line stops i just end up with a blank / grey window as in the below example screenshot. Doesn’t matter how long you leave the mouse pointer hovering over it, it never displays. If you then click the “Quick Look Attachment” that displays ok, just not the Preview.
However if i then move my mouse away from the pdf attachment and then move my mouse straight back over the attachment again, the pdf preview then displays.
So seems to be some issue displaying the pdf preview “when first hovering over the attachment” after the dotted lines stop. Replicated this same problem on another Mac with Sequoia as well.