.NET Core program.cs and Startup.cs not hit

I have a big problem with an application. When I use IIS Express, everything works fine, but if I start the app with IIS (both with or without Visual Studio), the Program.cs and Startup.cs are ignored so the app is not working.

This happen both with .NET Core 2.2 and .NET Core 3.1 and also with Razor Pages or MVC projects.

The strange thing is that IIS was working until yesterday and I haven't done any changes, only a computer restart between two days. This both in my notebook and desktop PC.

I don't understand why but this is driving me crazy. Do you have any suggestions for solve the issue?

Program.cs

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>();
            });
}

Startup.cs

    public const string GenericCookieScheme = "XXX";
    public const string AuthSecret = "XXX";

    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.AddRazorPages(options =>
        {
            options.Conventions.AuthorizePage("/Pages");
            options.Conventions.AllowAnonymousToFolder("/Pages/Login");
        });

        services.AddSession();

        services.AddControllersWithViews().AddRazorRuntimeCompilation();

        services.AddSingleton(Configuration.GetSection("AppSettings").Get<AppSettings>());
        #region SERVER
        services.AddEntityFrameworkSqlServer()
            .AddDbContext<DbConfigContext>(options =>
            options.UseSqlServer(Configuration.GetConnectionString("ConfigContainer")));

        services.AddEntityFrameworkSqlServer()
            .AddDbContext<DbDataContext>(options =>
            options.UseSqlServer(Configuration.GetConnectionString("DataContainer")));

        services.AddScoped<ITenantProvider, TenantProvider>();
        services.AddScoped<IUserProvider, UserProvider>();
        services.AddTransient<IDbContextFactory, DbContextFactory>();
        DbDataContext.Init();
        #endregion

        #region AUTHENTICATION
        services.AddAuthentication(o =>
        {
            o.DefaultChallengeScheme = CookieAuthenticationDefaults.AuthenticationScheme;
            o.DefaultSignInScheme = CookieAuthenticationDefaults.AuthenticationScheme;
            o.DefaultAuthenticateScheme = CookieAuthenticationDefaults.AuthenticationScheme;
        }).AddCookie(options =>
        {
            options.AccessDeniedPath = new PathString("/Login");
            options.LoginPath = new PathString("/Login");
        });
        #endregion

        services.Configure<IISOptions>(options =>
        {
            options.AutomaticAuthentication = false;
        });
        services.AddSingleton<IHttpContextAccessor, HttpContextAccessor>();
    }

    // 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();

        var defaultCulture = new CultureInfo("it-IT");
        var localizationOptions = new RequestLocalizationOptions
        {
            DefaultRequestCulture = new RequestCulture(defaultCulture),
            SupportedCultures = new List<CultureInfo> { defaultCulture },
            SupportedUICultures = new List<CultureInfo> { defaultCulture }
        };
        app.UseRequestLocalization(localizationOptions);

        app.UseHttpsRedirection();
        app.UseSession();
        app.UseAuthentication();

        app.UseStaticFiles();
        app.UseRequestLocalization("it-IT");

        app.UseRouting();

        app.UseRouter(r =>
        {
            r.MapGet(".well-known/acme-challenge/{id}", async (request, response, routeData) =>
            {
                var id = routeData.Values["id"] as string;
                var file = Path.Combine(env.WebRootPath, ".well-known", "acme-challenge", id);
                await response.SendFileAsync(file);
            });
        });

        app.UseAuthorization();

        app.UseEndpoints(endpoints =>
        {
            endpoints.MapRazorPages();
        });


        using (var serviceScope = app.ApplicationServices.GetRequiredService<IServiceScopeFactory>().CreateScope())
        {
            var t = serviceScope.ServiceProvider.GetService<IHttpContextAccessor>();
            #region CONFIG CONTAINER
            if (!serviceScope.ServiceProvider.GetService<DbConfigContext>().AllMigrationsApplied())
            {
                serviceScope.ServiceProvider.GetService<DbConfigContext>().Database.Migrate();
            }
            serviceScope.ServiceProvider.GetService<DbConfigContext>().EnsureSeeded(env.WebRootPath);
            #endregion
            #region DATA CONTAINER

            var dbContextFactory = serviceScope.ServiceProvider.GetService<IDbContextFactory>();
            //var allTenants = serviceScope.ServiceProvider.GetService<SigfridAppConfigContext>().Tenants.First();
            var context = dbContextFactory.CreateDbContext(Configuration);
            if (!context.AllMigrationsApplied())
            {
                context.Database.Migrate();
            }
            //serviceScope.ServiceProvider.GetService<DbDataContext>().EnsureSeeded(Guid.Parse("A2DDFB53-3221-41E7-AD27-F3CD70EC5BAF"));
            #endregion
        }
    }