How can I fix this issue with Google Play purchases?

Every time I try to complete a purchase on Google Play, I get this error message: 'Something went wrong. Couldn't complete your purchase. Check that you have the correct country selected in your Play account.' I've tried using several different cards, but none of them work. The odd thing is that these cards worked before, and they still work fine for free trials. Has anyone else faced this issue? What can I do to fix it?