My boyfriend and I signed up for a joint account and recently requested the new card. Both of us had problems with declined transactions after receiving the card and after a bit of thought, realised we probably needed to activate our cards. The only way we found out how to do this was searching in help.
I feel like there should be a clearer option in the app about activating a new card - maybe a button next to the Freeze card option? As a side note, is it mentioned in the card carrier that you need to activate the card?