https://support.mozilla.org/en-US/kb/websites-say-cookies-are-blocked-unblock-them

You can try these steps in case of issues with web pages: You can reload web page(s) and bypass the cache to refresh possibly outdated or corrupted files. *hold down the Shift key and left-click the Reload button *press "Ctrl + F5" or press "Ctrl + Shift + R" (Windows,Linux) *press "Command + Shift + R" (Mac) Clear the Cache and remove the Cookies for websites that cause problems via the "3-bar" Firefox menu button (Options/Preferences). "Remove the Cookies" for websites that cause problems: *Options/Preferences -> Privacy & Security<br>Cookies and Site Data: "Manage Data" "Clear the Cache": *Options/Preferences -> Privacy & Security<br>Cookies and Site Data -> Clear Data -> Cached Web Content: Clear Start Firefox in <b>Safe Mode</b> to check if one of the extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) or if <b>hardware acceleration</b> or <b>userChrome.css</b> is causing the problem. *switch to the DEFAULT theme: "3-bar" menu button or Tools -> Add-ons -> Themes *do NOT click the "Refresh Firefox" button on the Safe Mode start window *https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode *https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems *https://support.mozilla.org/en-US/kb/enhanced-tracking-protection-firefox-desktop *https://support.mozilla.org/en-US/kb/trackers-and-scripts-firefox-blocks-enhanced-track