There might be a perception of lower maintenance requirement on the Nuvinci hub, since even if it is installed or adjusted improperly, it still shifts, and even with much of the shifting range unavailable, it won't be perceived as being broken.
It looks like the sudden lost of shifting range is a known issue with the Nuvinci hub, due to incorrect installation:
Nfinity 1 - FAQ - Service - nuvincicyling.com
Looking at the manual, it seems that the hub should be installed in full overdrive position:
http://www.nuvincicycling.com/_Resou...Nfinity_v3.pdf4.2 Resetting CVP to Full Overdrive
2. If the Nfinity Hub Interface is incorrectly installed, full ratio range on the CVP may be unavailable, and full overdrive will need to be reset