Why is the Read method on my custom JsonConverter not called?

When I debug the test below, the code hits the CanConvert method of the EmailadressenConverter class and that method returns true.

I was expecting the Read method to get hit next, but this never happens, resulting in an object that has null for property EmailZakelijk.

Why is the Read method not called?

I am using .NET 8, and this is my code:

public class EmailadressenConverter : JsonConverter<Emails>
{
    public override bool CanConvert(Type typeToConvert)
    {
        return base.CanConvert(typeToConvert);
    }

    public override Emails? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
    {
        var ctorEmail = "";
        var optionalEmails = new List<string>();
        var currentPropertyName = "";

        while (reader.Read())
        {
            if (reader.TokenType == JsonTokenType.EndObject)
                break;

            if (reader.TokenType == JsonTokenType.PropertyName)
            {
                currentPropertyName = reader.GetString()!;
                continue;
            }

            if (string.Equals(currentPropertyName, nameof(Emailadressen.PrimairEmailAdres), StringComparison.CurrentCultureIgnoreCase))
                ctorEmail = reader.GetString()!;
        }

        if (string.IsNullOrEmpty(ctorEmail))
            return null;

        return new Emails(ctorEmail); 
    }

    public override void Write(Utf8JsonWriter writer, Emails value, JsonSerializerOptions options)
    {
        writer.WriteStartObject();

        writer.WriteString(nameof(Emails.Email), value.Email.Value);
       
        writer.WriteEndObject();

        return;
    }
}

public class Emails
{
    public Emails(string primairEmailadres)
    {
        Email = new Emailadres(primairEmailadres);
    }

    public Emailadres Email { get; set; }
}

public class DummyMailClass
{
    public Emails? EmailZakelijk { get; set; }
}

public class EmailadressenJsonConverterTests
{
    [Fact]
    public void Deserialize_only_primair_emailadres()
    {
        var json = """
            {
                "emailZakelijk": {
                    "email": {
                        "value":"[email protected]"
                    }
                }
            }
            """;

        var options = new JsonSerializerOptions();
        //options.Converters.Clear();
        options.Converters.Add(new EmailadressenConverter());
        //options.Converters.Add(new EmailsConverterFactory());

        var dmc = JsonSerializer.Deserialize<DummyMailClass>(json, options);

        dmc.Should().NotBeNull();
        dmc!.EmailZakelijk.Should().NotBeNull();
        dmc.EmailZakelijk!.Email.Value.Should().Be("[email protected]");
    }
}

public partial record Emailadres
{
    public Emailadres(string value)
    {
        Value = value;
    }

    public string Value { get; private set; }
}