Problem using Apple Pay

Used the Apple Watch with Apple Pay successful once. Since then I have tried twice to use Apple Pay and been unable to make it work. Double pressing the button does not bring up Apple Pay it just shows the wheel of friends. This happens when I'm standing at the checkout counter. Later I can double click the button and up comes Apple Pay. Cannot figure out what happens when I'm at the checkout counter. Anyone else having this problem? Any suggestions on what I"m doing wrong?