Cors problem with .NET app and React despite cors configuration – Asp.net

I’m building a backend using microsoft technologies for the first time and I’m having trouble getting my back-end to communicate with my front-end (React). The HTTP requests coming from Postman are succesful, so I doubt it is a problem with the build. I’ve been following tutorials and solutions on Stackoverflow, but I’m still getting the following message:

CORS blocking error in the console

Here is my Program.cs file, if it can help someone find the problem in my configuration:

var myAllowSpecificOrigins = "_myAllowSpecificOrigins";
var builder = WebApplication.CreateBuilder(args);

// Add services to the container.
var Configuration = builder.Configuration;

builder.Services.AddControllers();
// Learn more about configuring Swagger/OpenAPI at https://aka.ms/aspnetcore/swashbuckle
builder.Services.AddEndpointsApiExplorer();
builder.Services.AddSwaggerGen();

builder.Services.AddDbContext<BlogContext>(options =>
{
   var connectionString = builder.Configuration.GetConnectionString("DefaultConnection");
   options.UseMySql(connectionString, ServerVersion.AutoDetect(connectionString));
});


builder.Services.AddCors(options =>
{
   options.AddPolicy(name: myAllowSpecificOrigins,
       builder =>
       {
           builder.WithOrigins("http://localhost:3000")
           .AllowAnyMethod()
           .AllowAnyHeader()
           .AllowCredentials();

       });
}
);

builder.Services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
               .AddJwtBearer(options =>
               {
                   options.TokenValidationParameters = new TokenValidationParameters
                   {
                       ValidateIssuer = false,
                       ValidateAudience = false,
                       ValidateLifetime = true,
                       ValidateIssuerSigningKey = true,

                       IssuerSigningKey = new SymmetricSecurityKey(
                           Encoding.UTF8.GetBytes(Configuration.GetValue<string>("JWTSecretKey"))
                       )
                   };
               });

builder.Services.AddScoped<IUserRepository, UserRepository>();

builder.Services.AddSingleton<IAuthService>(
   new AuthService(
       Configuration.GetValue<string>("JWTSecretKey"),
       Configuration.GetValue<int>("JWTLifespan")
   )
);

builder.Services
  .AddMvc().AddNewtonsoftJson(options =>
   {
       options.SerializerSettings.ContractResolver = new CamelCasePropertyNamesContractResolver();
       options.SerializerSettings.Converters.Add(new StringEnumConverter());
   });
       


var app = builder.Build();

app.UseCors(myAllowSpecificOrigins);

// Configure the HTTP request pipeline.
if (app.Environment.IsDevelopment())
{
   app.UseSwagger();
   app.UseSwaggerUI();
}

app.UseHttpsRedirection();
app.UseAuthorization();
app.MapControllers();


app.Run();

EDIT

I tried to allow all origins and got the following error (this is by calling localhost:5090 from client. With localhost:7090 the backend simply throw a network connection error.

Access to XMLHttpRequest at ‘http://localhost:5090/api/auth/login’ from origin ‘http://localhost:3000’ has been blocked by CORS policy: Response to preflight request doesn’t pass access control check: Redirect is not allowed for a preflight request.