If your page does not display the expected content, there are a few steps you can take to debug content delivery.
Check your activity or campaign code carefully. A typo or other error could cause the expected content not to display.
Use mboxTrace or mboxDebug to troubleshoot the mbox.
mboxDebug is especially useful when you are setting up Target on your page to make sure the mbox is firing and the cookie is being set. However, it does not go into the kind of detail that is useful when debugging content delivery. If your activity does not appear on your page or undesired content appears, use mboxTrace to examine and debug the page in detail.
Because mboxTrace and mboxDebug can expose campaign data and profile data to external parties, an authorization token is required. The token can be retrieved using the Target Classic tool or via an API call. The authorization token is valid for 6 hours.
To get the token from Target Classic, click Configuration > mbox.js > Edit, then click Request Authentication Token.
See the content delivery troubleshooting doc to know more: