Cloudflare and its absurd ‘your browser is out of date’ blocks are beginning to make Firefox unusable for me. I’m routinely having to switch to Chrome to use sites. I have the same plugins in Chrome, yet Chrome opens sites that are blocked by Cloudflare in Firefox.
I am using Cloudflare for my company’s website and have not faced this issue. Which version of Firefox are you using? Can you try opening it in Firefox Safe Mode the next time you encounter this issue? https://support.mozilla.org/kb/troubleshoot-firefox-issues-using-safe-mode