Please use the following help article for preliminary debugging : Debugging at.js I would suggest to make sure that the mbox call is being triggered correctly and make sure you are a part of the activity, This can be checked using the mbox trace.
Our next Adobe Target Skill Builder Webinar is right around the corner on May 5th, and will be presented by Adobe Target Product Management on migrating Adobe Target’s mbox.js to At.js. Check out this community discussion to register today. Hope you can make it!