Wanting to re-verify & re-purchase minecraft

Both of my teens have logged into their accounts & it won't them download at the library where they normally play. Both played yesterday (July 21, 2018). Instead it wants them to re-verify (which it won't let them do, says that it is sending an email but never does) & then wants them to re-purchase. I have receipts for both of the purchases, one has had theirs since 2016 & the other since 2017.