A while ago, Flickr changed their API to require HTTPS connections to be made. This causes the Flickr uploader in the Fonera firmware to break.
As of today, there is a hotfix available for firmware 18.104.22.168 that fixes this problem and makes the Flickr uploader work again. Installing it is simple: Just head over to the “Applications” page on the Fonera dashboard and install the hotfix that’s listed there. It should work right away.
Note that this fix is only available for the latest released stable firmware version, 22.214.171.124. If you’re running an older version, you’ll have to upgrade first. Furthermore, if you ever do a factory reset, you’ll have to reinstall the hotfix (which is also the only way to uninstall the hotfix).