ronk there must be something in the Flarum log file or system PHP log file.
If there really is nothing, enable debug mode in Flarum and look at the request/response using your browser development tools. The "0" that shows up without debug mode is generally because Flarums tried to parse the response as a JSON object, but it in fact contains an HTML error produced by the PHP runtime or a proxy server.
Based on those symptoms, it's very likely that the problem is still the display_errors configuration that I outlined in my first reply. Make sure this change has been applied to the correct configuration file.
