@Anonymous We understand that you are receiving a 404 error in postman when trying to access the swagger API service hosted on your web app.
This is normally caused by improper authentication from my experience. Can you verify if your web app has any authentication on it? If so, are you handling that properly in postman?
For example, if your web app is using AAD for auth, you would need to follow these steps to ensure you are able to get into your web app.