Why is OneDrive showing incorrect or missing thumbnails for my files?

1. Check if the file type is supported in OneDrive
2. Check if the file size is not too large for OneDrive to generate a thumbnail
3. Check if the file has been synchronized, or moved to a local folder, in which case OneDrive will not create thumbnails
4. Check if there is connection issue which is preventing OneDrive from generating thumbnails
5. Check the system performance, and if necessary, delete unnecessary files and clean up temporary files