Can't buy coin and VIP

Need help I can't buy any coin in game

Error massage
Your purchase could not be complete

The question is what should I do ?

Help pls want to buy 1600 coin

Does it say that you need to contact Apple Support?
If it does, you should. You can contact them by e-mail or phone. You may also start a chat with one of their support staff via the link in the Apple website for your country.
Just tell the Apple support employee to allow your purchases to be completed for Haypi Monster. When you contact them, they will ask you to wait for 30 minutes. During these 30 minutes, you should NOT be logged on to your App Store account. After that, the purchase should be available.

If you don't get the message saying you have to contact Apple support, you need to contact Haypi support, either in game or by e-mail (or even post in the topic in this section of the forum regarding this topic) for it to be solved.

Good luck!