I cannot use NPM proxy other server's web app

[D414Dea4]

I have two servers, which I call it server A and server B

Now I applied nginx proxy manager on server A and runs a simple web app. This web app can be proxy.

But when I runs the same web app on server B, the nginx proxy manager which runs on server A cannot proxy the same web app on server B.

I can use ip+port to access the web app on server B