This extension is great! I have been using it off and on for years.
The problem is YT is constantly changing its codes, so the developer is having to keep on top of the changes, so he can keep the extension working smoothly for everyone.
The problem lies with YT, not the developer, who is always working on a fix for users. So please, if this extension has worked well for you, but one day it doesn't, keep what I have said in mind.
The developer is a one-man show, so please leave positive reviews for him. He deserves them!