You should be able to add products to your plan. Can you share what type of plan you have and if you have purchased directly from Adobe or through a reseller. (You'll get this information from the Admin Console > Accounts tab). For Teams and VIP plans you can follow the instructions at https://helpx.adobe.com/enterprise/using/add-products-and-licenses.html
Let us know if I misunderstood your question. If you're seeing an error on the Admin Console, see if you can share a screenshot.