Cannot use Apple Pay at store that does accept Apple Pay for others

I am unable to use Apple Pay at one local store that accepts Apple Pay. I have no trouble using Apply Pay elsewhere. Some customers at the store, a high end grocer, are able to make Apple Pay payments with the same model of iPhone, the latest IOS version and Wallet software and the same bank's debit card. However, a significant number of other customers have the same problem I have. It is black and white. The people that are unsuccessful and always unsuccessful.

The behavior of the POS reader is odd. I usually open Wallet and provide the security login before attempting the transaction, although I have tried letting the phone bring up Wallet from scratch as well. In either case, an LED on the card reader briefly flashes but nothing happens. There is no rejection or error message. It is as though the Apple Pay request is not recognized at all.

The store theorizes that the payment network that Apple Pay is trying is use is not one that they support. But, how could that be if other users have the same type of debit card from the same issuing bank, the same model of phone, and the same software on the phone? I tried dropping and re-adding the card and that did nothing.

Can someone educate me about the variables that come into play, and what might be causing this very selective behavior? Using a credit card payment rather than Apple Pay at this one store is not a true hardship, but it takes 3-4 times as long in the checkout line. I get used to the convenience.