Cors issue

The site is accessible via the www prefix (www.wpovermind.com), and it's also possible to log in that way. However, the interface breaks because of a CORS issue. Firefox in particular doesn't seem to like it: Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at https://wpovermind.com/api/v1/sites/1171/uptime/ssl-status. (Reason: CORS request did not succeed). Status code: (null).