Poor Service and a long wait with no explanation

Went to Macdonalds in Florida to buy some food for my kids on the 26/04/2019 had the most horrible experience. Placed my order at the self service machine. My order number popped up on the board and then after a few minutes it dissapeared. When I went to enquire they said they were busy with the order. I waited for 45 mins until I enquired again and then they suddenly started to make up my order when I asked why it took so long the response was "I am busy" This is an establishment that I have been frequenting for years and suddenly I get this kind of service.