Thanks for the quick reply Lafunamor. When I wake the screen the HTC One M8 presents the lockscreen but does not enable NFC. I have to use the PIN to get passed the Lockscreen and only then is NFC available. It seems to be a security feature of the handset and it makes using apps like Trigger a bit awkward at times.

The NFC on my HTC One M8 is disabled when the screen is Off or Locked. therefore, I can't use the NFC Ring Unlock app. I know that I can overcome this if I root my handset but I really don't want to do that for a variety of reasons (for starters it would invalidate the warranty). Has anyone found a solution?