You may enable basic logging for tracking problems with the IPN by checking “Enable logging” in the extensions settings tab. This will create a log file for you in the plugin’s folder. As data is written to the log, it will be displayed on the plugin’s settings tab below the settings. Essentially, it will indicated the time of the transaction, the status, and the action (which should indicate the user ID and that the user’s expiration date was moved forward).
It is not recommended that you continue to use the log file on a live system once you know you have things functioning. This is primarily for debugging potential IPN issues. You should use it when using the sandbox, and maybe when you first set up live transactions just to verify you are working.
You can clear the log file by checking the box “Clear Log File” and submitting.
When you are finished with the log file, you can delete it. Turning off logging will also remove the log file.
In instances where a complete log of all IPN information is needed (usually only in the case of troubleshooting difficult issues), “verbose” logging can be enabled using the wpmem_exp_ipn_defaults filter hook.