In case of problems, enable the internal logger

<nlog internalLogFile="c:\log.txt" internalLogLevel="Trace">
   <targets>
      <!-- target configuration here -->
   </targets>
   <rules>
      <!-- log routing rules -->
   </rules>
</nlog>

In case of problems, enable the internal logger.

C# example:

// set internal log level
InternalLogger.LogLevel = LogLevel.Trace;

// enable one of the targets: file, console, logwriter:

//  enable internal logging to a file (absolute or relative path. Don't use layout renderers)
InternalLogger.LogFile = "c:\\log.txt";

// enable internal logging to the console
InternalLogger.LogToConsole = true;

// enable internal logging to the console (error stream)
InternalLogger.LogToConsoleError = true

// enable internal logging to the Trace
InternalLogger.LogToTrace = true

// enable internal logging to a custom TextWriter
InternalLogger.LogWriter = new StringWriter(); //e.g. TextWriter writer = File.CreateText("C:\\perl.txt")