Make sure no Addons are blocking and accepting cookies.

"You don't have permission to access..." errors are characteristic of a firewall that protects the server against misuse and this firewall thinks something is suspicious about the HTTP request. If you use a proxy or VPN then try to use a direct connection. You can try to clear the Cache and remove the Cookies for websites that cause problems via the "3-bar" Firefox menu button (Options/Preferences) to see if that fixes it. I've also seen cases where having "Resist Fingerprinting" enabled caused this issue to occur. *https://support.mozilla.org/en-US/kb/firefox-protection-against-fingerprinting If this all doesn't work then you can try "Forget About This Site" in the right-click context menu of an history item.