The NTP31 (NTP30) was originally designed to use the Gelion 39 refill. Schneider has recently discontinued the Gelion 39 and replaced it with Gelion+. To adapt to this change, Nitecore redesigns part of the NTP31 to make it compatible with both the new Gelion+ and the discontinued Gelion 39. However, the original NTP31 manufactured before this change around Mar.2021 only works with the Gelion 39.
The users of the original NTP31 can still use the other refills in the compatibility image including the Parker ones.