You can only redeem rewards when you have completed the registration of your card. For this, you normally received an email to confirm the link of your card. As soon as the link is confirmed, you can start redeeming rewards again.
Didn’t receive the email or deleted it by mistake? Go to https://my.joyndev.kinsta.cloud/card-registration and enter your email address and card number. The registration email will be sent again as soon as possible so you can still link your card.