NLog IValueFormatter do not output any data?

I have the following IValueFormatter :

public class NLogValueFormatter : IValueFormatter{    public bool FormatValue(object value, string format, CaptureType captureType, IFormatProvider formatProvider, StringBuilder builder)    {        if (value.GetType() == typeof(LogData))            return false;        builder.Append(format);        try        {            var myTarget = LogManager.Configuration.FindTargetByName("communicationFileLog");            myTarget = ((myTarget as NLog.Targets.Wrappers.WrapperTargetBase)?.WrappedTarget) ?? myTarget;            var jsonLayout = (myTarget as NLog.Targets.TargetWithLayout)?.Layout as NLog.Layouts.JsonLayout;            if (jsonLayout?.MaxRecursionLimit > 0)            {                var jsonSettings = new JsonSerializerSettings() { MaxDepth = jsonLayout?.MaxRecursionLimit };                using (var stringWriter = new StringWriter())                {                    try                    {                        using (var jsonWriter = new JsonTextWriterMaxDepth(stringWriter, jsonSettings))                            JsonSerializer.Create(jsonSettings).Serialize(jsonWriter, value);                    }                    catch (Exception) { }                    builder.Append(stringWriter.ToString());                }            }            else                value = null;        }        catch (Exception ex)        {            builder.Append($"Failed to serlize {value.GetType()} : {ex.ToString()}");        }        return true;    }}

The goal with this is to do a JSON serializationthat I can set depth on.

This line of code is executed at statup :

NLog.Config.ConfigurationItemFactory.Default.ValueFormatter = new NLogValueFormatter();

To log data I got this code :

public void LogCommunication(CallInformation callInfo)        {            _comLogger.Log(LogLevel.Info, "ComLogger : {@callInfo}", callInfo);        }

In Nlog.config I got this :

<logger name="CommunicationLogger" minlevel="Trace" writeto="communicationFileLog"></logger><target xsi:type="File"            name="communicationFileLog"            fileName="${basedir}/logs/${shortdate}.log"            maxArchiveDays="5"            maxArchiveFiles="10"><layout xsi:type="JsonLayout" includeAllProperties="true" maxRecursionLimit="1"></layout></target>

I can see that the FormatValue is executed but the builder contents seems to never end up in the logfile. I do however get some kind of standard serialization in the file but I dont know where it comes from, meybe the includeAllProperties=true. It is not respecting the maxRecursionLimit anyway.

How do I get the IValurFormatter to put out text to the file instead of the standard one?

Regards