It doesn't work for me. Restarted firefox, uninstalled and reinstalled, restarted again, no dice.

Firefox blocks this extension.
I have uninstalled and reinstalled, but no luck.

developer sold out to avast

"This extension hides automatic sign-in pop-ups on Youtube."

Not any more it doesn't. It worked once, on first use, and hasn't hidden the sign-in nag since.
Uninstalled.