Internal URL link

I have a tunnel setup to access an internal application. We do not use the WARP client, it is simply a URL that our users connect to using website(dot)domain(dot)app which tunnels to website(dot)domain(dot)org.

This app works fine, but there is a subset of users that need to access a separately hosted application that is linked to this app, so they click on a link from within website(dot)domain(dot)app which attempts to load newsite(dot)domain(dot)org.

I have created a self hosted site in my tunnel for this second site (newsite(dot)domain(dot)app) but I cannot get it to work together.

I hope I am explaining this properly. Any help is apprecited.