The most straightforward way to implement cart abandonment is as follows;
In any case, you should absolutely be able to use Trace, and trace end in the trace tool, to see everything happening.
A couple of notes;
1. When using trace end, it may take one minute or so for the "Visitor Session Ended" message to appear in the UDH trace UI, whereupon you will then see all the enrichments and actions you have configured.
2. Do you have a delay on your connector action? i.e. Something like "Is In Audience At End of Visit, and delay action by 2 hours"? If so, trace will show a message similar to what you are reporting here, I believe. For debugging, I recommend removing the delay first, tracing that and verifying that the connector sends the data correctly, and then re-instating the delay.
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