Failing to reason or explain to customers instead they choose to ignore them , without assistance

On the 25th of November 2022, i was at McDonald's Dobsonville i wanted to redeem a deal that i had of Mcfeast on my McDonald's app, i asked one of the employee Nomonde for assistance , she came there tried scanning my IQR code on their machine and it didnt go through , another employee called she just left me standing and went to that employee, i stood there waiting for her to come back and she didn't, i had to go to her , and she said the system was not working and there is nothing she can do about it , i asked her about the message that appeared on the screen that reads "error has occurred call a manager for assistance " she said there's nothing the Manager can do if it says that , what a response , she didn't apologize or tried any means to help me she just left me there once again .... what an experience wouldn't advice one to go there to enjoy their especially using an app or IQR codes.