How to troubleshoot local SQL connections in a Blazor App from Visual Studio 2019 - sql-server

Question

Learning Visual Studio 2019, C#, and SQL on my local PC. Having trouble connecting to the local SQL databases and making sure that my app opens up in my local browser.
Now an app that has previously worked fine gives me a 404 error. I cannot figure out why this is happening. In general I would like to have a tool or some other checklists to see why the server is throwing the error.
Would love to have some advice on best ways to do this.
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I should have added code and better explanation initially.
I am rebuilding an app. Started with a fresh Blazor server app project, and started moving things over from the old app. I was eventually able to compile the new app and then launched it and originally got an SQL error.
Now I can get the app to launch a browser window (tried both Chrome and Edge) but nothing displays at all, it just looks like it is loading. There is nothing I can see in the console or in output. No errors. When I debug everything seems fine, the code never hangs on any line. Nothing ever errors out.
I can rebuild again but I want to figure out how to troubleshoot issues like this.
Startup.cs
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Wire_Desk.Data;
using Syncfusion.Blazor;
namespace Wire_Desk
{
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.
// For more information on how to configure your application, visit https://go.microsoft.com/fwlink/?LinkID=398940
public void ConfigureServices(IServiceCollection services)
{
services.AddRazorPages();
services.AddServerSideBlazor();
services.AddSingleton<WeatherForecastService>();
services.AddSyncfusionBlazor();
}
// This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
{
if (env.IsDevelopment())
{
app.UseDeveloperExceptionPage();
}
else
{
app.UseExceptionHandler("/Error");
// The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
app.UseHsts();
}
app.UseHttpsRedirection();
app.UseStaticFiles();
app.UseRouting();
app.UseEndpoints(endpoints =>
{
endpoints.MapBlazorHub();
endpoints.MapFallbackToPage("/_Host");
});
}
}
}
Program.cs
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Hosting;
namespace Wire_Desk
{
public class Program
{
public static void Main(string[] args)
{
CreateHostBuilder(args).Build().Run();
}
public static IHostBuilder CreateHostBuilder(string[] args) =>
Host.CreateDefaultBuilder(args)
.ConfigureWebHostDefaults(webBuilder =>
{
webBuilder.UseStartup<Startup>();
});
}
}
I don't know what more code I should include. When I debug once I get through the program file and step into, there are no more code to step through, although this was also true with a small sample app.
I am stumped.