youtube viseos will not run on firefox but will on chrome and firfox private

Since YouTube works in a Firefox Private Window, I’d suspect something in your normal Firefox profile rather than Firefox itself. Try clearing YouTube’s site data first: '''Settings → Privacy & Security → Cookies and Site Data → Manage Data''', search for '''YouTube''', remove it, then restart Firefox. If that doesn’t fix it, try Troubleshoot Mode. If YouTube works there, an extension or custom setting is likely causing it.