Trying to load but never does

[BiglifeMatt]

This screenshot shows the site trying to load but never does.

This server is on the same primary domain but different subdomains. It is also on another virtual server but they are on the same subnet.

[littlecoce]

I have the same problem but as far as I can tell, serving Nextcloud and Roundcube from different domains is not possible at this moment. NC just displays RC-Interface as iframe which in turn tries to alter/access DOM-Elements from the main site. This is just a layman's guess.

You can change your INSTALL_DIR/config/config.inc.php and add the line:
$config['x_frame_options'] = 'ALLOW-FROM https://YOUR-NC.DOMAIN.HERE';

Keep in mind that this X-Header is old and deprecated by the Content-Security-Policy frame-ancestors (see here).

With the old header set the sidebar loads at least although not in the full size. Don't expect any functionality though as click-jacking protection prevents you from actually using the frame.

After a few hours I haven't found a working CSP config. Maybe someone else can shed some light on this topic?