Nlog does not write log file to Windows service

I have a windows service written in .net 4.0 and I installed it under Local System credentials. In the code I used nlog,

private static Logger logger = LogManager.GetCurrentClassLogger();
logger.Debug("some information");

      

        
        
        
      

    

I also have nlog.config copied to the same directory where the exe file is located

<?xml version="1.0" encoding="utf-8" ?>
<nlog xmlns="http://www.nlog-project.org/schemas/NLog.xsd" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <targets>
    <target name="logfile" type="File"
            fileName="c:\log\TestService\My.log"
            layout="${longdate}::${logger}::${message}"
            keepFileOpen="false" />
  </targets>

  <rules>
    <logger name="*" minlevel="Info" maxLevel="Deubg" writeTo="logfile" />
  </rules>
</nlog>

      

        
        
        
      

    

But if I start the service, I don't see the log file generated at all. If I change the code log.Debug

to Debug.WriteLine

and use my Visual Studio to attach to Windows processing for debugging, I see that there is my debug message in the output window, which means my Windows service code is correct.

Is there a problem with my nlog code?

- Update 1 -

I have updated nlog.config to

<?xml version="1.0" encoding="utf-8" ?>
<nlog xmlns="http://www.nlog-project.org/schemas/NLog.xsd" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <targets>
    <target name="logfile" type="File"
            fileName="c:\log\TestService\My.log"
            layout="${longdate}::${logger}::${message}"
            keepFileOpen="false" />
  </targets>

  <rules>
    <logger name="*" minlevel="Trace" writeTo="logfile" />
  </rules>
</nlog>

      

        
        
        
      

    

and changed my code to

logger.Trace("some information");

      

        
        
        
      

    

then it works. I'm not sure what is wrong with my first config.