That's a symptom of a not yet correctly established link that happens when you try to use the theme without a working bridge, not the underlying problem. As Elmer stated, the exact error that XLink ran into when trying to establish the link is logged under internal_data/xlink_errors on your XenForo installation.Edit: This seems to be the underlying problem:
<b>Fatal error</b>: Uncaught Error: Class 'XF' not found in /var/www/html/wp_blog/wp-content/themes/wp-xpress-theme/front-page.php:18
Has anyone else experienced the Class 'XF' not found in ...front-page.php:18 before?
The line in question in that file is:
XPress::app()->registry()->set('xpress', array_merge($registryValues, ['title' => \XF: phrase('thxpress_home')]));