Rated 1 out of 5 stars
This is a non-working extension. Supposedly, there's a fixed version on their website. Not the way extensions for FF are supposed to be used!
Waiting for the fix to download from the official Mozilla addons site. Why? Because these are checked by AMO editors for safety. It's too easy to be tricked into going off-site - a typical social-engineering scheme - and getting a potentially compromising extension. Not that DownloadHelper would, but why would you want to encourage that sort of bad and risky behavior? Put the updated fix here on Mozilla! Until then, no stars (okay, only 1, because there's no way to put no stars).
Since you read the add-on developer's comments, instead of installing the fixed version, why don't you just take the first option: go the add-on preferences and check again the "Extended download menu" as it was before you changed it. This will also fix your issue.