It looks like a recent Windows update related to Office 365 has broken the thumbnail display of Serif files (Photo, designer, but also Draw Plus). It took me some time to figure it out, but Explorer now display a little sync status symbol with each file that is synchronised with OneDrive. And since then, Thumbnails for Affinity files have disappeared.
The attached pictures show how the file is displayed (large icon setting) in a OneDrive-synchronised folder and in a local folder.
This update does not affect standard file formats such as JPEG, PNG, PDF with preview etc.
The orange dot on the local file is the Carbonite online backup sync status. You will notice that this one is also gone with the O365 update...
It would be nice if you could fix this feature in a future update...
Kind regards,
Jean Gerrekens