The client sees the following message: You already have an unpaid order for this bundle.

This means the client has already ordered this bundle once and the order is still awaiting payment. You can check the payment status of the order in Orders in the left sidebar of your admin (column Payment status).

This serves as a safeguard to prevent duplicate orders without payment. Until the previous order is either paid or cancelled, the client cannot purchase the same bundle again.

However, the client can still purchase a different bundle.