The link you posted (replacing xxx) works on my end, but my guess is that it's some kind of regional update or layout change of some kind that causes it to fail for you... Can you contact me through one of the links at the bottom of https://addons.mozilla.org/en-US/firefox/addon/image-max-url/ ? (Unfortunately it's not possible to have a back and forth with firefox reviews)

Hopefully we can fix this :)