Could you please send us the log files from the Host and the Viewer? Here's how to locate the log files: Host logs and the Viewer logs. You can send them to [email protected]. Please do not publish the logs on the forum, they are considered personal information.
The RU Server is not related to http(s), so the nginx configuration is not necessary. You can set up the RU Server on any machine with an external IP address and create a subdomain record in your DNS with a subdomain that points to this IP address.