The 'free version' is referring to Cloudscraper. FFNet bumped up Cloudflare a level or two (not sure if permanent or not) and the developer of Cloudscraper puts that level behind a subscription model. Jim's looking into alternatives.
If you at least want access to the fic and it's not crossposted to AO3 (search both the title and author), the standalone
FanFictionDownloader (no relation to the old version of FFF) uses a different method of scraping and is reported to be working.