Thumbnails not showing

This is great plug-in. I have the image uploads going directly to a Nextgen Gallery. The upload process works fine. However, the image thumbnail do not show unless I clear the image cache in Nextgen. Is there a reason for having to do it or is there a setting or way to show the thumbnail after it is uploaded?

https://ww.wp.xz.cn/plugins/nextgen-public-image-uploader/