Google Images recently updated, and the previous technique to find the original images past 100 (the preloaded amount) doesn't work anymore. I've implemented a fix for the userscript version, but unfortunately getting this to work on the extension version is a bit trickier, and might not land in the next release (it needs to intercept HTTP calls, which is definitely my least favorite approach towards supporting a website).
I've tracked the feature here: https://github.com/qsniyg/maxurl/issues/1533 . Note that once it's implemented, you will need to enable "Rules intercepting HTTP requests" (under the Rules tab). It's disabled by default because it carries a fingerprinting risk.