Why is my WebApplicationFactory hanging for 5 minutes before timing out?

I'm trying to add some integration tests to my existing .net 6.0 project, but keep running into issues

Right now if I run the test, it hits the line await host.RunAsync(CancellationToken.None); in Program.cs and then just hangs forever and seemingly does nothing

Have I misunderstoof something? If not how can I troubleshoot this?

Program.cs

public /*static*/ class Program
{
    public static async Task Main(string[] args)
    {
        var host = BuildWebHost(args);

        await host.InitialiseAsync(CancellationToken.None);

        await host.SeedAsync(CancellationToken.None);

        await host.RunAsync(CancellationToken.None); // hangs here
    }
}

Tests.cs

[Fact]
public void Test1Async()
{
    using (var application = new WebApplicationFactory<Program>()
        .WithWebHostBuilder(builder =>
        {
            builder.ConfigureServices(services =>
            {
                // set up servises
            });
        }))
    {
        var c = application.CreateClient(); // hangs here
    }
}

It does eventually time out and give me this error

Message:  System.InvalidOperationException : Timed out waiting for the entry point to build the IHost after 00:05:00. This timeout can be modified using the 'DOTNET_HOST_FACTORY_RESOLVER_DEFAULT_TIMEOUT_IN_SECONDS' environment variable.

Stack Trace:  HostingListener.CreateHost() <>c__DisplayClass10_0.b__0(String[] args) DeferredHostBuilder.Build() WebApplicationFactory1.CreateHost(IHostBuilder builder) DelegatedWebApplicationFactory.CreateHost(IHostBuilder builder) WebApplicationFactory1.ConfigureHostBuilder(IHostBuilder hostBuilder) WebApplicationFactory1.EnsureServer() WebApplicationFactory1.CreateDefaultClient(DelegatingHandler[] handlers) WebApplicationFactory1.CreateDefaultClient(Uri baseAddress, DelegatingHandler[] handlers) WebApplicationFactory1.CreateClient(WebApplicationFactoryClientOptions options) WebApplicationFactory`1.CreateClient() UnitTest1.Test1Async() line 35