Failed to connect to localhost/127.0.0.1:5000

I am using Retrofit2 to make network requests but the endpoint is locally on my machine.

So my base URL is private val BASE_URL = "http://localhost:8000/", but it gives me this response Failed to connect to localhost/127.0.0.1:5000

So I did some search and I found out that I need to use my local IP address as the following private val BASE_URL = "http:192.168.1.15//:8000/", but then I get this response Response{protocol=http/1.1, code=404, message=Not Found, url=http://192.168.1.15//:8000/api/Home/RegisterShop}

Any idea how to solve this issue?