Blazor Server localization not. Cannot find resources - localization

Question

My goal is to add localization to my Blazor Server application so I can change the language.
I followed this tutorial and first tried to integrate this in a new project. This worked fine.
Then I wanted to integrate the code into my actual application. Unfortunately this does not work.
The problem seems to be that it can't find the resources.
I tried it again with two new applications and found out that it is because of the hyphen in the name. I think that this causes problems because the hyphen in the namespace is replaced with an underscore.
Both applications are server side in the .NET 6.0 framework.
One is called EMV and the other E_M_V as project and solution name.
The code I have added:
Added the Resources folder with the resource files: App.resx.
You only need one to recreate the problem. The problem is not the switching of the language, but that it takes the value from the given key.
I have a key called TestString and the value says This is a Test.
I have installed Microsoft.Extensions.Localization (7.0.0) and added it in the _Imports.razor.
This is my Program.cs. I commented which three parts I added:
using EMV.Data;
var builder = WebApplication.CreateBuilder(args);
// Localization
builder.Services.AddControllers();
builder.Services.AddLocalization(options => options.ResourcesPath = "Resources");
// Localization
builder.Services.AddRazorPages();
builder.Services.AddServerSideBlazor();
builder.Services.AddSingleton<WeatherForecastService>();
// Localization
RequestLocalizationOptions GetLocalizationOptions()
{
Dictionary<string, string> cultures = builder.Configuration.GetSection("Cultures").GetChildren().ToDictionary(x => x.Key, x => x.Value);
var supportedCultures = cultures.Keys.ToArray();
var localizationOptions = new RequestLocalizationOptions()
.AddSupportedCultures(supportedCultures)
.AddSupportedUICultures(supportedCultures);
return localizationOptions;
}
// Localization
var app = builder.Build();
if (!app.Environment.IsDevelopment())
{
app.UseExceptionHandler("/Error");
app.UseHsts();
}
app.UseHttpsRedirection();
app.UseStaticFiles();
// Localization
app.UseRequestLocalization(GetLocalizationOptions());
app.MapControllers();
// Localization
app.UseRouting();
app.MapBlazorHub();
app.MapFallbackToPage("/_Host");
app.Run();
My Index.razor looks like this:
#page "/"
#inject IStringLocalizer<App> Localizer
<h3>#Localizer["TestString"]</h3>
This setup works totally fine in one project and not in the other. It only displays the resource key name.
I don't know if this is a bug or if I have to direct the ResourcesPath differently in my Program.cs