There are different reasons why a product voucher has the status "waiting for confirmation" if the offer is set up with automatic confirmation.
No more appointments are stored in the offer / offer is deactivated
Product vouchers are only valid for a specific offer (article number) and a specific ticket category (ticket option). If the offer and the price list for which the voucher is valid to have dates stored in step 4 of the offer creation for today or in the future, the customer only receives those for selection and this date is then confirmed as specified in the offer (manually or automatically).
If nothing more is stored for this price list or the offer is deactivated, then the customer can suggest an appointment of his choice and the request has the status "Waiting for confirmation".
Every available appointment is sold out
If there are no more appointments available, the customer is able to suggest a new appointment. In this case, the status is 'waiting for confirmation', too.