adding to what Diva says, we do need to see the page!
1) Does the image show in other browsers
2) Are the other product images on the site working
3) Does the original image have an uppercase file extension eg image.JPG, and what happens if you replace the image with one with a lowercase extension
4) Did the image show before installing Image handler?
5) What happens if you change
Admin --> configuration --> IH small images filetype
from no_change to jpg
and do the same for
Admin --> configuration --> IH medium images filetype
Admin --> configuration --> IH medium large filetype
Bookmarks