"Snapshot Processing Failed" After Uploading Atlas Page

[Zian]

After uploading the following atlas page, the Field Papers website said:

Snapshot Processing Failed (Smaller Atlas.png)

Unfortunately, your snapshot for image Smaller Atlas.png failed to be processed. It's possible that it was an intermittent error, in which case you should try re-uploading. If the problem persists, please open a GitHub issue or email help[at]fieldpapers.org with details.

URL: https://fieldpapers.org/snapshots/15j31r2f

This image was created by reducing the original 6458 pixel by 4958 pixel (10.76 inches x 8.26 inches) image with Paint .NET.