App Store payment failure for free or paid apps on child's iPad

When going into the App Store on his iPad he’s 7 btw I can’t download any free or paid apps. Says payment failed. I checked some forums says a purchase failed but I have checked his and my account and can’t see anything and I have a valid card attached to the system

[Re-Titled by Moderator]

Original Title: my sons ipad can no longer downlload games etc from app store. i have checked and no failed