It took me a bit to locate the button to push to launch the extension (blue block with an F inside, up at the top right for me).
Once I found it, it's worked great, something like 98% of the time. I have encountered a few reels that are running on my screen, but when I click, it thinks for a bit and says there is something wrong with the reel that is being displayed. Almost all the other reels from the Facebook page download flawlessly.

I don't know, maybe the field that receives the URL needs to be a bit longer and it's truncating the URL?

Otherwise, highly recommended!