Have you added the 'Watch Configuration' to your Service assembly?
e.g. using XML configuration
log4net.Config.XmlConfigurator.ConfigureAndWatch(
new System.IO.FileInfo("log4net.config"));
e.g or the DOMConfigurator (deprecated?) assembly attribute
[assembly: log4net.Config.DOMConfigurator(Watch=true)]
When my appenders aren't working, it's normally this step I've forgotten!