Hi guys,
I’ve just tried to buy a TFL 7 day travelcard online (I have enough credit) but the Monzo card was declined, however TFL active card check went through.
Anyone with TFL online experience?
It may help people answer if you clarified if you refer to the beta prepay card or new current account card
If you’re using the Beta cards, check that your billing address in TfL matches the one shown in the app and contact us through in-app chat. It’s an easy fix on our end. 
Yep, that worked. Thanks!