A pineapple error means that you're trying to enter a bank account that is already in use. Benefit does not allow two different Benefit accounts to share one payment method. This is for fraud prevention and also because banks will reject purchases, thinking they are duplicates.
Pineapple errors typically occur when spouses or family members are looking to pay for their Benefit cards with one bank account or credit card.
Instead, both users should login with the same Benefit account from two separate phones. With this arrangement, not only are the payment accounts shared, but when a card is purchased it will appear on both phones sharing the same account.
We will be looking to add support for shared payment accounts for different users in the near future.