Try the following steps in order to resolve the issue: 
  1. In the pricing section of the group sale, confirm the pricing is per ticket.  Discounts cannot be applied to any flat rate group sales reservations, even if the flat rate is per ticket for extra people.
    1. To discount the flat rate group sale, adjust the price of the flat rate to reflect the discount.  Edit the pricing on the reservation to reflect the new flat rate price.  Then, go back into the flat rate and readjust the price to reflect the normal pricing.
      1. Go to Sales > Group Sales > Group Sales Settings > Flat Rate Pricing tab.
      2. Click on the flat rate that is on your reservation.
      3. Click Edit rate scale.
      4. In the Prices section, edit the price to deduct the discount.
      5. Click Save.
      6. Go back to the group sale reservation.
      7. In the pricing section, click Edit pricing structure.
      8. Select per ticket and click Save.
      9. Click Edit pricing structure and select Flat Rate and select your flat rate scale.
      10. Click Save.
      11. Go to Sales > Group Sales > Group Sales Settings > Flat Rate Pricing tab.
      12. Click on the flat rate that is on your reservation.
      13. Click Edit rate scale.
      14. In the Prices section, edit the price to the original flat rate price.
      15. Click Save.
  2. Determine what is creating the balance on the group sale.  If the only balance on the sale is from a resource or facility (location), the discount will not apply.  Discounts do not apply to resources or facilities.  Instead, you can change the price of these by clicking on it, then clicking override cost.
  3. In the pricing section of the group sale, click Edit and change the pricing to Flat Rate, then click save.  Then edit again and change it back to per ticket to refresh the group sale pricing.
    1. Go to the group sale reservation.
    2. In the pricing section, click Edit pricing structure.
    3. Select per ticket and click Save.
    4. Click Edit pricing structure and select Flat Rate and select your flat rate scale.
    5. Click Save.