Seems like I am experiencing the same thing.
I tried image-store v3.2.0 and was able to upload images to galleries and create albums. Image files created were confirmed by looking through FTP.
When I create a page with a short code such as [image-store] all the thumbnails images are broken.
I have tried enabling permissions to 777
I have enabled image hotlinking on the server
I think the issue lies with image.php
P.S. the above link doesn’t work.
Hope you can clear up this issue, the plugin is awesome.