Currently when publishing containers in FootPrints 12.1.XX - 20.XX, you may not find enough details to identify and troubleshoot the problem or error. Additional details are stored in the Footprints.log file on the Footprints application server. Please follow these steps to review the log using the available log viewer. In FootPrints 12.1.XX - 20.XX and higher, there is a new option to download the Footprints.log file to your workstation and  launch the log viewer.
 

In FootPrints 12.1.XX - 20.XX, you have the download and log viewer option.
 

1. Download the Footprints.log.zip file and unzip to a local folder on your workstation
2. Launch the log viewer and load the log file from your local drive.

The Footprints.log file will rename itself and start a new file when it reaches 10 MB in size, so you may need to look at an older file to find the time when the error happened.

You can also use this tool to determine information from the incoming email debugging, publishing errors, business rule execution, or other occurrences that could be affecting FootPrints 12.1.XX - 20.XX.

NOTE: A new feature in FootPrints 12.1.XX - 20.XX summer release is the option to enable sending browser errors to the server log.  Please go into Administration>System Management>System Settings>Server Configuration page. If you are troubleshooting an error in the browser, enable the "Logging Configuration" setting to "Send browser error to the server log".
 

I do not recommend turning on the "Custom Logging Configuration" unless you receive instructions from BMC Software Footprints support.

NOTE: When turning on the "Email Debugging", for tracking incoming email processing, the data is written to the footprints.log file.  To turn on email debugging, go to the Administration>System Management>Email Settings>Incoming Email (System) page for the option at the bottom of the page to "Enable Email Debugging".  I do not recommend leaving on due to the extra logging can affect performance over time.
 

Using Custom Logging

Please use this article to gather the current custom login options:
Package filters list and tips for version 12.x

See the BMC Communities post for additional comments and ideas on troubleshooting.
How to troubleshoot FootPrints 12.1.XX - 20.XX using the footprints.log?
https://communities.bmc.com/docs/DOC-35426
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In FootPrints 12.0 you will need to use these steps to access the log file and log viewer.

1. Go to the Footprints Service Core application server.
2. Go to the C:\Program Files\BMC Software\FootPrints Service Core\web\default folder.
3. Launch the "fp-log-viewer.html" in a browser on the server. You may have to give it permissions to run and open pop-up windows.
4. Click the "Load Log" icon.
5. Change the "Minimum log level to load" to "Warn".
6. Click the link to "Browse" to "Load from a file".
7. Go to the C:\Program Files\BMC Software\FootPrints Service Core\logs and select "footprints.log".
8. Double click to see full details of the error.