Hello. Why i can't make an in-app purchases?
We are fellow users here on these forums, we won't know unless you give us some info as to what happens when you try to make IAPs e.g. does the 'buy' button not work, do you get any error messages ... ?
If you are getting a message to contact iTunes Support then you can do so via this link and ask them why the message is appearing (we won't know why) : http://www.apple.com/support/itunes/contact/ - click on Contact iTunes Store Support on the right-hand side of the page, then Purchases, Billing & Redemption
If it's a different problem ... ?