Hi there yubag,

You may want to verify that your account is designated as an aprrover (parent/guardian). Take a look at the article below for more information. 

Designate another approver (parent/guardian)

The organizer can also give another adult in the group permission to manage Ask to Buy requests. Go to Settings > iCloud > Family and tap their name. Then tap Parent/Guardian. Only one adult needs to manage each purchase, and after it's done, the purchase is final.

Request and make purchases with Ask to Buy

-Griff W.

That is definetly odd. At this point, you may find more information by using another one of Apple's support resources - https://getsupport.apple.com/

-Griff W.