Bad service

I am an avid MacDonald's foodie today I downloaded the app today and then claimed a Double cheese voucher ref OFFER 864 704. I then went to MacDonald's ChrisHani Crossing, a security guard asked me for my order before I got to the pay window which I understood since the was no intercom.

Upon my arrival at the window a lady with crew ID 168 N. Nkuna told me the voucher scanner was not working and has not been working for some time. My question was why is it not fixed then? since the are still vouchers on the app. Her response was because of the Covi-19. Which I know is untrue because, The same ChrisHani branch once told my wife she can only claim vouchers twice. I ended up paying the full amount for a double cheeseburger.

Are these vouchers only for selected for specific branches and what is the redeem limit?