NFC not picked up by phone

Hey,
Just got my pucks this morning and am really enjoying them so far, I just hit one snag with NFC, my phone (Nexus 6P) will not pick up the device via NFC, by comparison I have some other NFC tags (whiztags) that are working as expected.

I've tried the following:

• out of the box NFC config (ie redirect to puck site) isn't picked up by the phone
  

• explicitly setting a new url with NRF.nfcURL isn't picked up by the phone

  NRF.nfcURL("http://espruino.com");
  

I have updated the firmware to 1v89 (one thing with the instructions there is that to select the firmware zip with nRF Connect on Android you have to press and hold on the firmware zip rather than just press - that threw me for a while).
/John