Imagine the screen showing the sweet spot is a guide and try the ring in adjacent areas as well.
Also note that you do have at least 2 out of 3 known difficult devices.
Which ring did you get on kickstarter? There are two types.
The Normal or "Classic" ring is a thinner band at 7mm than the Alpha band at ~13mm.
The Alpha and Classic can behave differently when used, and the Alpha can be slightly more easily read by a phone with misbehaving NFC.
I find that most people who are having read issues are suffering under the misconception that the ring will work the same as a plastic NFC fob or swipe card. It does not.
It's been known all along that the NFC Ring will have a shorter read distance and be more difficult to read than a standard single tag device in a non-metallic housing will be. This was actually one of the selling points on kickstarter.
Unfortunately this can mean that a device with NFC which is not functioning optimally will be a confusing and irritating experience.