"Invalid Token" when trying to validate account in .NET Core 7 app

I have check a lot of resources about this problem but none applies to my case.

I am using this code to generate the token that is sent in the e-mail:

string token = await _userManager.GenerateEmailConfirmationTokenAsync(user);
var callbackUrl = $"{_request.Scheme}://{_request.Host}{_request.PathBase}/Authenticate/Security/ConfirmEmail/{user.Id}?token={WebEncoders.Base64UrlEncode(Encoding.UTF8.GetBytes(token))}";

When e-mail is received and clicked the link, this code is run:

var user = await _userManager.FindByIdAsync(userId);

if (user is null)
    return new Result { Success = false, Errors = new Dictionary<string, string[]>() { { "NotFound", new string[] { "Usuario no encontrado " } } } };

IdentityResult result = await _userManager.ConfirmEmailAsync(user, Encoding.UTF8.GetString(WebEncoders.Base64UrlDecode(token)));

When debugging, I can check that the token generated by

string token = await _userManager.GenerateEmailConfirmationTokenAsync(user);

is exactly the same after running

Encoding.UTF8.GetString(WebEncoders.Base64UrlDecode(token))

I am in the same development machine, so the MachineKey problem is not the cause. I am using user time stamp, but it is correctly set and never changed.

Since generation is made by GenerateEmailConfirmationTokenAsync and validation is made by ConfirmEmailAsync, the purpose of the key is the same, and equal to Confirmation.

What else can I check?

Thanks

It turned out that I am using a custom user store. When I loaded the ApplicationUser, I forgot to set the security stamp field.

Now, when loading the user, I am using this method to set the properties:

    private static ApplicationUser? GetUserData(Usuario? u)
    {
        if (u == null)
            return null;

        return new ApplicationUser
        {
            Id = u.UsuarioId,
            UserName = u.UsuarioLogin,
            FirstName = u.UsuarioNombre,
            LastName = u.UsuarioApellido,
            PhoneNumber = u.UsuarioTelefono,
            PhoneNumberConfirmed = u.UsuarioTelefonoConfirmado,
            Email = u.UsuarioEmail,
            EmailConfirmed = u.UsuarioEmailConfirmado,
            PasswordHash = u.UsuarioPasswordHash,
            SecurityStamp = u.UsuarioSecurityStamp
        };
    }

Of course, the method is called from public async Task<ApplicationUser?> FindByIdAsync(string userId, CancellationToken cancellationToken) of custom user store.

Cheers
Jaime