Mcdonalds Bruma.....*******

I am a loyal Mcdonalds customer, but today i was let down by Mcdonalds...I use the Mcdonalds app & got a redeembale coupon for a Spicy Cajun for only 90c, so i went to Mcdonalds Bruma close to eastgate & wanted to redeem it, the cashier called the manager named Gladys who told me they cannot redeem it, i showed her the expiry dates and terms & conditions of the coupon which were all fine, she in turn told me the owner of the Mcdonalds told them not to redeem during month end periods, yet the app does not disclose any of these details, the app is useless i dont know why they still run it. i engaged with Mcdonalds today at 11:20 am within the coupon terms n conditions, the store had 1 customer with about 3 tills open so it wasn't busy.