Can't sign into iTunes store
I have family sharing set up. My daughter has an old iPhone which we've reconfigured to be associated with her Apple ID. One app (YouTube) needs to be updated. When we try to update, it prompts to "Sign in to the iTunes store", NOT the app store where she's already logged in. It asks for a password, but doesn't say for which account (hers, mine as the family admin, or my wife who used to own the phone). I've entered all passwords but none work. We reset her iCloud password and it still doesn't work. I've opened up the iTunes store but nowhere does it say which account the device is signed into iTunes with or offer a way to change it.
iPhone 6s