I've got to disagree on that one, if the seperate tags work but have to be in a sweet spot then there are issues with the NFC in your devices. I would say to contact support@nfcring.com and query the possibility of a swap from Classic to Alpha (assuming you have a Classic ring to start with).
I would say that for whatever reason you are simply having NFC reading issues whether it's a method based issue or straight out poor NFC in your devices.
From the other thread "Inlays on their own, without metal, will be extremely easy for a phone to read. If you need to find a sweet spot for an inlay that is not in a ring then your phone has issues which will require your attention."
The rings will behave differently due to their construction, being made of metal.