There are multiple possibilities for this. Please check the following options:
- Is there a mistake in the configuration of your voucher categories?
- Has the expiration date of your voucher code or category already been reached?
- Has the contingent of your voucher codes already been exhausted?
- Is there a spelling mistake in the voucher code you’ve used?
In case any of those options apply, please change your configuration or adjust your handling and try again.