Apple Pay 'hold near reader' - iPhone 8Plus

My iphone 8Plus is about a week old. Worked day 1 at Whole Foods when I paid with Apple Pay; then two variables were introduced...I put a case on it, and I think I did a software update. Now Apple Pay just says "hold hear reader" when I attempt to use at Whole Foods, and Raley's. Both locations worked fine for my previous iPhone SE. Is there a difference in the NFC antenna on the 8Plus? Could it be the update I installed? I've restarted the phone; it shouldn't be the card, because the same card worked on day 1.