If a recurring donation is missing a credit card, a warning will popup. The warning will happen if an original profile that had a StripeID was merged into a different record and the ID was deleted. CommunitySuite does not save credit card information, but it does save the StripeID that will be seen on a profile's record. The StripeID must be there for CommunitySuite to have a credit card charge.
To add the credit card on a recurring donation, click the Add Creditcard button on the donation in the left-side menu, which will direct you to Stripe. Alternatively, you can have the donor start a new recurring donation online and delete the old one.