Samsung Galaxy S4 is not connecting with supermarket NFC.

[AC Question]

It connects sporadically, but lately not at all. What am I doing wrong?

 

[Rukbat]

Are you? Or is the store? That's the first thing that has to be diagnosed. (Stores are notoriously bad at installing new electronics - it can take them months to get the bugs out. Sam's Club, after many months of trying, gave up on having Android phones scan purchases as they were made - they could never get a phone to connect to the system to check the purchase list out.)