Don't keep it secrete... What were you doing before you got the message? Do we need to login to replicate the issue? Did you try Firefox in Safe Mode? https://support.mozilla.org/en-US/kb/diagnose-firefox-issues-using-troubleshoot-mode#search104 What security software are you running?

Trying to log in to twitch,then I get the message this browser not supported,no I didnt try safe mode as twitch loses functionallity ,was working fine before the latest firefox update

Can at least login in Troubleshoot Mode?