Why am I being asked for my Billing Address again on the App Store?

Hello, I've been having a problem recently where it takes to enter my billing address when I try to download something. When I do, the boxes are marked red and the top says to enter all the info after I press continue. I've checked all the boxes multiple times to make sure all the info is correct (which it is) and have no idea why it's doing this. Any help would be appreciated as I am still a bit new to technology.