I use android pay when it's available in the US, but the first time you encounter any specific reader, there's a learning curve. By "reader", it should be obvious we mean the reader that is in the store that you tap your phone or slide your card into, not the fingerprint reader on your phone.

Most of them look like this: https://en.wikipedia.org/wiki/Payment_terminal#/media/File:P... and will occasionally have a contactless payment icon or an apple/android pay logo on the screen when you walk up to it. In the case of this card reader, the NFC point is at the bottom of the screen and you basically have to rub your phone on the screen to get it to read.

Sometimes they look like this one: https://www.flickr.com/photos/jeepersmedia/14128014654 but that big pad at the top is a lie - those have never actually worked and if there's not a sign on it, the cashier will tell you it's "broken".

The rest of them look like this: https://twitter.com/dionlisle/status/768124197549723648 and there's no clear indication or consistency where the NFC contact point is, or it is also a lie and you shouldn't even bother.

I'd say about half of my credit card transactions these days involve me handing a card to someone who swipes it directly into the register - there's no way to possibly use NFC or enter a PIN for debit/etc.