Cannot verify payment information
I can’t put in my information country Serbia so I can't put the correct information only the USA region, and now I can't buy the application
Try these support articles.
How to Fix “Verification Required” for Apps Downloads on iPhone and iPad
Or you can click the blue Edit payment methods in the article below. When signed in and the page loads, you will be on the credit card page. After updating that, click the Go Back button at the lower left and you will be on the address page.