Worst experience ever - Dainfern

I walked in to the branch at Dainfern with the intention of getting a pre workout. The sales assistant there tells me that I cannot pay with my card because those items are not on the system so I need to pay with cash. I didn’t have cash so I walked out empty handed.

How is it possible that you put something on the shelve but a customer cannot buy it because they are not “loaded on the system” and how does cash only solve that problem?