I've created an express object called publications. I'll be out-putting the entries in a list sort-able by topic. I wanted to use the C5 in-built topic object, so I built a tree with nodes, and then added it as an attribute to the publication express object, then of course added it to the express form.

It doesn't work however. When I add or edit a publication, I can click on a node in the topic tree, but nothing is saved or passed into the database. Nothing shows up in output, anywhere. The field topic shows up, but has no value.

What am I missing?

Screenshot attached.