ASP.NET Core 8 Web API Cors blocked only into POST

Question

This is my Program.cs file:

using BackendTemplate.Utils;
using Microsoft.AspNetCore.Authentication.JwtBearer;
using Microsoft.IdentityModel.Tokens;
using System.Text;

var builder = WebApplication.CreateBuilder(args);

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

builder.Services.AddAuthorization();

builder.Services.AddCors(o => o.AddPolicy("MyPolicy", builder =>
{
    builder.WithOrigins("*")
           .AllowAnyMethod()
           .AllowAnyHeader()
           .AllowAnyOrigin();
}));

var app = builder.Build();

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

app.UseHttpsRedirection();

app.UseCors("MyPolicy");
app.UseAuthentication();
app.UseAuthorization();

app.MapControllers();

app.Run();

This is my controller

[HttpPost]
public ApiResponse<string> Post([FromBody] UsrUser user)
{
    // .....
}

Only the POST generates a CORS error; the GET works correctly.

This is my error on Angular console:

Access to XMLHttpRequest at 'https://mydns/api/login' from origin 'http://localhost:4200' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource.

I cannot understand how to solve this problem, is the first time this happens to me.