The ninth arcanum is about the closed door. Someone in the lineage could have helped and did not; took help and gave nothing back; walked past when asked outright.
A descendant recognises this by the fact that help reaches them at the wrong moment. There are people around, but at the hard moment they are not there; their own efforts on behalf of others go unnoticed; a feeling accumulates that they owe everyone and nobody owes them. Often the person themselves does not know how to give thanks: the words seem superfluous, and so they are never said.
The working-off is to help without counting on anything back and to say thank you out loud. Not for the large things, but for the ordinary ones. This is the most everyday of the twenty-two laws of the lineage, and that is exactly why it is the hardest to work off: it consists not of deeds but of the daily habit of noticing other people.