Custom product fields not showing on client summary

Hi

I have 3 custom fields for a particular product, filled in. When I do a license check using the WHMCS Licensing Addon, I get a return for those fields. But, when I do a "getclientsproducts" api call, those fields have nothing in the value.

A check of the client's summary page under the products tab also shows no values for the custom product fields.

How can I get these to populate with the values that are present for the product?

Using WHMCS v. 5.2.16.