Are you currently using a version from the repositories of your Linux distribution? Try the Firefox version from the official Mozilla server: https://www.mozilla.org/en-US/firefox/all/ Make sure you are not blocking content. [https://support.mozilla.org/en-US/kb/diagnose-firefox-issues-using-troubleshoot-mode Diagnose Firefox issues using Troubleshoot(Safe) Mode] {web link} A small dialog should appear. Click '''Start In Troubleshoot(Safe) Mode''' (not Refresh). Is the problem still there? --------------- https://support.mozilla.org/en-US/kb/enhanced-tracking-protection-firefox-desktop Many site issues can be caused by corrupt cookies or cache. '''Warning ! ! ''' This will log you out of sites you're logged in to. You may also lose any settings for that website. * [https://support.mozilla.org/en-US/kb/delete-cookies-remove-info-websites-stored Delete cookies to remove the information websites have stored on your computer] {web link} * [https://support.mozilla.org/en-US/kb/how-clear-firefox-cache How to clear the Firefox cache] {web link}acking-protection-firefox-desktop

Note that this is about running Firefox on RPi 4 and not Firefox on desktop. Can you resolve this host on the DNS Lookup tool on the about:networking page ? Can you try a different DNS service ?