Daughters Apple ID unable to purchase apps since ios11 update

My daughter (who is on Family Share) has an iPhone 6s and we recently updated it to iOS11. Ever since then, her AppleID has been acting very strangely in both app store and itunes. Whenever she attempts to purchase an app (even a free one), a prompt comes up to put in her password (saying "Sign-In Required"). We put the password in correctly, and it button shifts from "Get" to a circling icon which circles for a few seconds, only to return to the get button. We know that we are putting in the correct password, because when we put in the incorrect password we get a "Verification Failed" box and it asks us to try again or cancel. The same thing happens in the iTunes store where when you try and purchase a song, the $1.29 price button changes to a circling icon after we enter the correct password...and then it just changes back to the $1.29 button.

I get a similar type experience when I go into settings - touch ID and Passcode and attempt to enable touchID for iTunes and App Store. It asks for the password, and when we enter it correctly, it looks like it is enabled for a few seconds, and then automatically shifts it back to disabled.

This AppleID works just fine on her iPad which we haven't updated to ios11 to yet. In fact, we can purchase apps on the iPad, and then go to the iPhone app store and go to the purchased section and download the app just fine there. It only seems to be the actual purchase process that seems broken.

I haven't had this issue on any of my other family accounts when upgrading. I have tried to download all the recent updates (up to 11.1) hoping the problem would get fixed, but no such luck. I have changed her password and it didn't fix it. I reset the phone and restored it, and have the same issue.

Any ideas or people facing the same issue?