This does happen sometimes with unstable Internet. I had the experience recently. I just delete the file and re-upload. That worked fine and I haven't had the experience since. To delete the blank thumbnail, click on it to highlight it and click on the trash can icon on the right side of the page.
You could try what I did and see how it works for you. Let us know if it does.
That has been reported before. Indeed, deleting and reuploading may help. If the issue continues, you should check the file, may be opening in Illustrator and resaving may help. Do not, however, overwrite the original file in this case.
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ABAMBO | Hard- and Software Engineer | Photographer
This does happen sometimes with unstable Internet. I had the experience recently. I just delete the file and re-upload. That worked fine and I haven't had the experience since. To delete the blank thumbnail, click on it to highlight it and click on the trash can icon on the right side of the page.
You could try what I did and see how it works for you. Let us know if it does.