All websites that are added to ScreenCloud Signage are automatically checked to make sure that they display properly on our players.
For internal websites, we are unable to access the sites to check them. Therefore, it's up to you to make sure that the site has no restrictions, otherwise, the players will remain blank when trying to load the page.
One thing you can check is, our player loads external websites into an iframe (a sandboxed one for security reasons). The page you're trying to add might have an 'X-Frame-Options' header set to 'SAMEORIGIN' which means we can't load it into our iFrame.
Please check to see if this is the restriction on the website.
If so, you can either remove the options altogether or set as X-Frame-Options: ALLOW-FROM https://screen.cloud.