ArcGIS Monitor Log Parser for IIS
It sounds like you are trying to integrate "System Log Parser for IIS" with ArcGIS Monitor. I recommend running SLP for IIS as a standalone tool first to verify it is working before integrating it to ArcGIS Monitor. Click on the "SystemLogsGUI" application to launch it as a standalone application. See image below:
Verify you have met the requirements to access the IIS logs on the remote machine as per the inline help:
If the IIS logs are on a remote machine, you will need to map a network drive in Windows first (eg. \\ettvm30.esri.com\c$ or \\eslsrv10.esri.com\inetpub) with read permissions before your user can browse to it.
In short, to read the IIS logs from the ArcGIS Monitor machine where you are running (testing) SLP for IIS as a standalone program, you must share the IIS logs as a network drive and the Windows account you are using must have read permission. Likewise, the Windows account running the ArcGIS Monitor service must have read permission.