Whenever I try to sign into my youtube it goes to a page that says "Your browser's cookie functionality is turned off. Please turn it on.". I came here for help, and so far everything it has said to do has done nothing for me.
Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance).
Do NOT click the Reset button on the Safe Mode start window or otherwise make changes.