How to associate Trading Partner Item with child organization

Summary:

I am able to create and associate a TPI with the Master Organization. However, I cannot add an association to a child organization, and the TPI won't appear for the child organization.

Content (required):

Am I missing a setup that will enable me to associate a trading partner item at the child organization?

Version (include the version you are using, if applicable):

21C

Code Snippet (add any code snippets that support your topic, if applicable):