Relate field does not show related record

Running SuiteCRM 8.5 on a Ubuntu Server 23.10 VM (Azure).

I have created a custom module, Sponsors, which is related to the Accounts module.

Sponsors have a relation field; Accounts have a subpanel.

When I click “Create” in the Sponsors subpanel in the Accounts module, I can create the record just fine. It saves and is displayed in the subpanel as expected.

But in Sponsor’s detail view, the Accounts relation field is blank. No information. I can make changes and the Sponsors record continues to be shown in the Accounts subpanel.

What’s wrong here? How can I get the relation field to show the correct Account?