How to forward to other web pages with web forwarding

I'm currently creating a website with node.js and I'm using ngrok to make it public. I have registered a domain for forwarding to the URL generated by ngrok, so that the users can access to the node.js website by entering a domain e.g. http://www.example.com.

However, when I tried to visit another web page (http://www.example.com/login), it would always display the main page while URL remains the same (still displays as /login). but it works perfectly if I do the same thing with the URL of ngrok. so what should I do to make the web forwarding works for other web pages?

Thanks!