Purchase issue – account marked as underage by mistake

Hi, I can't make any purchases in FC Mobile. I keep getting a message saying I need to log in, even though I’m already properly logged in. This issue never happened before. I'm also getting a message that I’m underage, but I confirm that I’m over 18. It's possible that I accidentally selected that I’m underage — please change my birth year to reflect that I’m an adult. I really want to buy a specific offer, but I can’t because of this issue. Please help me resolve it. Thank you!