For more information on troubleshooting platform errors, please take a look at the Troubleshooting section of XLink here.
No XLink Platform link has been established, the previous platform link has been deleted or the XPress or XLink XenForo add-on is unavailable (disabled/uninstalled). Please ensure both add-ons are active and configured.
This issue is usually accompanied by dozens of Cross-Origin errors in the browser console and happens when XenForo and WordPress are run on different subdomains.
In order to run XPress in a subdomain setup, the Cross-Origin mode in the XLink platform settings has to be enabled, and the server has to be configured to allow resource sharing between both subdomains. Your server host should be able to resolve the situation with the errors logged in the browser console.
When running XenForo and WordPress on different subdomains, XenForo cookie domains have to be configured in a way that cookies are available on both subdomains, otherwise session information cannot be shared.
This issue usually happens when WordPress is installed in a subfolder within your XenForo installation. The given problem is that your server is passing the request to the first index.php file that accepts it, starting at the root folder (XenForo). As XenForo accepts any arbitrary request, and doesn’t understand the request, it throws a 404 page. Your server host should be able to change the server configuration to have it pass the request to the subfolder first.
WordPress plugins that rely on jQuery usually load an older version of jQuery, which will be overwritten by XenForo’s jQuery version later on, subsequently eliminating the already loaded version and hence crashing the JavaScript of your plugins. Enabling the JavaScript Wrapper mode in the XLink platform settings will normally resolve this issue.