NodeJS API service is not consistent on proxy/firewall enabled network

Am coming here with a great hope of getting some help to the issue that I am facing more than a month now.

We have developed a website which is developed in Angular 6 and Node JS (ExpressJS).

The website is loading perfectly on our device and other open networks. But we had to run the website in a university where they had proxy and firewall enabled. So When we hit the website in the lab we found that our node api service is not consistent. Most of the time our api responds with a response as

The site can't be reached right now

So here is the list of thing that we tried to resolve this issue

  1. We tried testing our NODE API with http://.. instead of https://.. , it worked. So we thought the issue is related to the SSL certificate.
  2. But then we realized that if SSL Certificate was an issue, my website should have not been loaded. Our website is getting called except the rest API that we have created using nodejs seems to be a problem.
  3. We tried to implement NGINX, but that did not help us either.
  4. We tried changing our node API port as we though university server might be blocking the port, but even after changing ports it did not work.

But this is something related to HTTPS. As HTTP API services are working perfectly fine. We are using httpsServer in the express node to allow https calls from the client side.

Is there something that we need to do in NodeJS to overcome such issue? Because if a firewall or proxy was an issue then other websites such as coursera, youtube should have behaved in the same way. But the problem is somewhere on our end and hence am looking for an experienced people to help me out with the issue.

We tried searching everywhere not just stack overflow but other sources. And we tried most of them but we were unlucky to find the solution here.

Thank you