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Hey! This is somewhat of a common issue with strange configuration issues with specific machines. Especially on Macs. Our engineers have identified three possible causes and solutions for this issue: Highly sensitive anti-virus software. The way to get around this is to whitelist moz.com in the software. If you are running Sophos Anti-Virus on Mac. Disable the option 'Block malicious downloads from websites, protecting your Mac from obfuscated, polymorphic and zero-day threats before reaching your browser'. Enterprise firewalls that block us, which you may need to work with your IT department on if you do not have direct access to your firewall settings. VPN connection/profiles. Disabling or removing the VPN profile has been known to be a common issue. We confirmed that the problem was the Cisco AnyConnect client installed on his machine. Even if the client isn't actively running, a background service it installs blocks CORS requests. Uninstalling it allowed him to use MA immediately. Here's an article describing the problem, and a possible workaround: http://www.bennadel.com/blog/2559-cisco-anyconnect-vpn-client-may-block-cors-ajax-options-requests.htm Ultimately our guess is a software update is compromising key security files that are preventing access to ajax options requests and a last resort fix has been a re-install of an OS. It's very tricky but hopefully one of the above issues is the culprit, which can be fixed. Hope this helps!