Cannot get a Blazor Server App to call a secure downstream Web API using Azure AD B2C

I created a new blazor server project using dotnet new

dotnet new blazorserver --output "PlayingWithBlazor" --framework net6.0 --auth IndividualB2C --aad-b2c-instance "https://{mytenant}.b2clogin.com/" --domain "{mydomain}.onmicrosoft.com" --client-id "{myClientID}" --susi-policy-id "B2C_1_SignUp" --called-api-url "https://localhost:7042/api" --called-api-scopes "https://{mytennant}.onmicrosoft.com/a82e00f8-939d-47ab-b2f3-4e557020f729/access_as_user"

When I run the app using Visual Studio, I can log in using my AAD B2C user flow. However, when I click on "Call Web API" it throws an exception at await downstreamAPI.CallWebApiForUserAsync in CallWebAPI.razor

The @Code block for CallWebApi.razor that was autogenerated with the project looks like this:

@code { private HttpResponseMessage? response; private string? apiResult;

protected override async Task OnInitializedAsync()
{
    
    try
    {
     
        response = await downstreamAPI.CallWebApiForUserAsync(
                "DownstreamApi",
                options => options.RelativePath = "/Subscriber");

        if (response.StatusCode == System.Net.HttpStatusCode.OK)
        {
            apiResult = await response.Content.ReadAsStringAsync();
        }
        else
        {
            apiResult = "Failed to call the web API";
        }
    }
    catch (Exception ex)
    {
        ConsentHandler.HandleException(ex);
    }
}

Here is the Exception:

Microsoft.Identity.Web.MicrosoftIdentityWebChallengeUserException
  HResult=0x80131500
  Message=IDW10502: An MsalUiRequiredException was thrown due to a challenge for the user. See https://aka.ms/ms-id-web/ca_incremental-consent. 
  Source=Microsoft.Identity.Web
  StackTrace:
   at Microsoft.Identity.Web.TokenAcquisition.<GetAuthenticationResultForUserAsync>d__16.MoveNext()
   at Microsoft.Identity.Web.DownstreamWebApi.<CallWebApiForUserAsync>d__5.MoveNext()
   at PlayingWithBlazor.Pages.CallWebApi.<OnInitializedAsync>d__3.MoveNext() in C:\Users\AndySchneider\source\repos\PlayingWithBlazor\Pages\CallWebApi.razor:line 33

  This exception was originally thrown at this call stack:
    [External Code]

Inner Exception 1:
MsalUiRequiredException: No account or login hint was passed to the AcquireTokenSilent call. 

My Web API is pretty plain vanilla right now.

// GET: api/<SubscriberController>
        [Authorize]
        [HttpGet]
        public IEnumerable<Subscriber> Get()
        {
            return subscriberRepository.GetAllAsync().Result;
        }

From what I have gathered, it looks like Microsoft.Identity.Web is calling MSAL. Everything I have found so far in troubleshooting an error like this leads me to catching MSAL exceptions and working with AcquireTokenSilent. Because I am not using MSAL directly, I am not sure where I would need to go to add this error handling, or what to add , for that matter.

For what its worth, here is my Program.cs as well

using Microsoft.AspNetCore.Authentication;
using Microsoft.AspNetCore.Authentication.OpenIdConnect;
using Microsoft.Identity.Web;
using Microsoft.Identity.Web.UI;
using Microsoft.AspNetCore.Components;
using Microsoft.AspNetCore.Components.Web;
using PlayingWithBlazor.Data;
using Microsoft.AspNetCore.Authentication.Cookies;
using Microsoft.AspNetCore.Diagnostics;
using Microsoft.AspNetCore.Http.Extensions;
using Microsoft.Identity.Client;

var builder = WebApplication.CreateBuilder(args);

// Add services to the container.
var initialScopes = builder.Configuration["DownstreamApi:Scopes"]?.Split(' ');

builder.Services.AddAuthentication(OpenIdConnectDefaults.AuthenticationScheme)
    .AddMicrosoftIdentityWebApp(builder.Configuration.GetSection("AzureAdB2C"))
        .EnableTokenAcquisitionToCallDownstreamApi(initialScopes)
            .AddDownstreamWebApi("DownstreamApi", builder.Configuration.GetSection("DownstreamApi"))
            .AddInMemoryTokenCaches();

builder.Services.AddControllersWithViews()
    .AddMicrosoftIdentityUI();


builder.Services.AddAuthorization(options =>
{
    // By default, all incoming requests will be authorized according to the default policy
    options.FallbackPolicy = options.DefaultPolicy;
});

builder.Services.AddRazorPages();
builder.Services.AddServerSideBlazor()
    .AddMicrosoftIdentityConsentHandler();
builder.Services.AddSingleton<WeatherForecastService>();

var app = builder.Build();

// Configure the HTTP request pipeline.
if (!app.Environment.IsDevelopment())
{
    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.UseAuthentication();
app.UseAuthorization();

app.MapControllers();
app.MapBlazorHub();
app.MapFallbackToPage("/_Host");

app.Run();