How to fix "Error 404 Operation not found" in Azure API Management Self-hosted Gateway

Question

I'm encountering an issue with my self-hosted gateway in Azure API Management. For development, I've deployed the gateway on my laptop using a Docker container at http://localhost:8089.

I've set up an ASP.NET API hosted in IIS at https://api.test.local (I set this URL as the backend in APIM). However, when I try to send a request using Postman (e.g. http://localhost:8089/test-api/clients), I receive the following error:

404 Resource Not Found/Operation not found

I hosted another ASP.NET API in IIS which ran at https://localhost:4045, but when I set it as the backend address in APIM, it doesn't work.

As a solution I bound the address of the API to an IP address in IIS, http://192.168.63.10 and this works. For some reason it doesn't work if I use a domain name. I also tried to host the Echo API on the self-hosted gateway, but then I also got this error:

Error 404: Resource not found

Here are the settings of the API:

What am I missing here?