React Native: Calling API running on localhost

I have an API that I'm running locally on my machine. I'm trying to access this data in a development environment and running into issues.

When I have my React Native app running through expo, localhost is referring to the devices localhost and not the one running on my desktop. I have researched this quite a bit and the top suggestion is to query your internal IP address instead of localhost.

When I query localhost I get an exception thrown with no details:

Network request failed

When I query my internal IP, the request hangs and nothing happens.

I'm starting expo through this command: expo start --tunnel

Here is the code making the request:

fetch("http://localhost:5001/api/standings")
    .then((res) => console.log(res))
    .catch((err) => console.log(err))

The .NET API works through chrome. On both localhost and my internal IP (with a warning about an unsecure connection).

I there any additional configuration I'm missing?

EDIT:

Here is the Postman response:

Here is my Startup.cs

public class Startup
{
    public Startup(IConfiguration configuration)
    {
        Configuration = configuration;
    }

    public IConfiguration Configuration { get; }

    // This method gets called by the runtime. Use this method to add services to the container.
    public void ConfigureServices(IServiceCollection services)
    {
        services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_1);
        services.AddHttpClient();
        services.AddCors();
        services.AddEnv((builder) =>
        {
            builder
            .AddEnvFile(".env")
            .AddThrowOnError(true)
            .AddEncoding(Encoding.ASCII);
        });
    }

    // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
    public void Configure(IApplicationBuilder app, IHostingEnvironment env)
    {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }
        else
        {
            app.UseHsts();
        }

        app.UseCors(builder =>
        {
            builder
            .AllowAnyOrigin()
            .AllowAnyMethod()
            .AllowAnyHeader()
            .AllowCredentials();
        });

        app.UseHttpsRedirection();
        app.UseMvc();
    }
}