A cart can only be switched to a member when it contains subscription items only (Weekly Subscription plan or subscription meals). If the cart holds anything from another module — meal packs, à-la-carte meals, catering, extras bought outside a subscription, gift cards, etc. — the switch is refused with Please clear your cart before switching to a member account. Empty the cart (or finish that order first), then select the member again.

The reverse also applies once a member is selected: adding non-subscription items shows Please clear your cart before adding other items., and adding subscription items to a cart that already has other items shows Please clear your cart before adding subscription items.