Turn on log4net's internal logging.

Per midpage in this, you will need something like so in App.config:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
   <startup/>
   <appSettings>
      <add key="log4net.Internal.Debug" value="true"/>
   </appSettings>
   <system.diagnostics>
      <trace autoflush="true">
         <listeners>
            <add name="textWriterTraceListener"
                  type="System.Diagnostics.TextWriterTraceListener"
                  initializeData="C:\temp\log4net.txt" />
         </listeners>
      </trace>
   </system.diagnostics>
</configuration>