In order to connect your iPhone to the NFC Reader you will need to use the Lightning Port to Audio Jack Adapter.

It's a small lead so if you don't use plug in headphones with your iPhone, you may have not seen it in the iPhone box yet.  Please see a picture of what the cable looks like below.

If you don't have one, you will need to purchase a genuine Apple Lightning to 3.5 mm Headphone Jack Adapter from Amazon or www.apple.com
 

* Please note this troubleshooting guide is for existing customers only.  With effect from Jan 26, 2021 we no longer issue or sell external NFC Readers to connect to iPhone 6 and below or iPads.