User can't connect to Portal or sees a different page instead

Portal is accessible through port 80 (HTTP), or 443 (if SSL is enabled), just like a regular web server. HTTP/HTTPS traffic needs to be allowed through the server firewall(s) in order for the web interface to be accessible from the outside. In addition, a public IP access is required if players and users are to connect to it over the internet.

If there is already a web server installed on the server, such as IIS or Apache, make sure that you either stop these services or rebind them to a port other than 80/443. Then, restart the DISE services.

https://support.dise.com/solution/articles/9000144102-restart-windows-services

If the server had one IP address when it was installed and then was changed to another, run the file "C:\Program Files (x86)\DISE\DISE Server\DISEServerInstaller.bat" and set the new IP. 

I keep losing my connection to DISE Server

Please check the results from this page: "Real-Time Web Test - Does HTML5 websockets work for you?" (websocketstest.com). Websockets are tunneled through port 80 (or port 443 if SSL is enabled).
Reasons that sockets may still be unable to connect are:

• Aggressive packet filtering on the router.
• Virus protection software that blocks non-encrypted web sockets.