The push notifications sometimes give more detailed information than the transaction list in the app: “Declined: ATM withdrawals deactivated” or something like that.
Location based security sometimes can be a bitch when the phone did not update location informations because it was offline and data roaming is deactivated.
Are you guys using iOS devices? I would close and reopen the app, force the phone to use some location based things …
Sorry, no more ideas here. If there isn’t a general IT problem with a card processor, the security settings are the only thing I can think of here. I would try contact Revolut via Twitter.