Creating a ComboCart where person A purchases a subscription for two or more other people

Using the REST API, we are trying to create a ComboCart which will allow person "A" (a non-company administrator) to purchase a non-dues subscription (journal) for two or more other people "B" and "C".

When we make the ComboCart sold to party, person "A". They cannot checkout as the cart says "You do not have permission to purchase this item".

Eliminating the sold to altogether throws an error when viewing the cart (likely a 500)

We have tried several combinations to achieve this with no luck.

Is this even possible?

Thanks,

Randy