If you're one of the few stores still on the old product page layout you'll find that the latest version of ShopifyFD (link to extension) will no longer work on product pages. I've created a LEGACY version that should help cover you in the meantime. Do note that this version is only intended to be a short term fix and not something you should plan on using long term. As soon as you see the new product page layout you should start using the official one again.
Link to Legacy Version
For reference, the new product page layout looks like this: