In-app purchases will only appear within the Parents profile and not inside the Child profile or Kids+. Unfortunately, this is an Amazon Kids+ attribute that affects all apps with In-App purchases such as our Budge apps and is out of our control. We've already contacted Amazon to report this issue, however, there is little that we can do until they change this policy. You can play the app in the parent profile, in the meantime.
We understand how frustrating this situation is and suggest that you contact Amazon directly with your comments: https://www.amazon.com/gp/help/contact-us