With the introduction of Sinnoh region Pokémon into the popular mobile app, players will also be able to get Sinnoh region evolutions through the use of Sinnoh Stones. But while they once were considered a guaranteed weekly reward, it now seems that they will be randomly generated.
We first saw the Sinnoh Stones last month, when Niantic ran an egg-hatching event in Pokémon GO. The stones allowed users to evolve their previous generation Pokémon into the newly added 4th gen evolutions. At the time, Niantic stated that players could acquire these stones by completing a full seven days worth of research tasks.
Now there have been several reports by players that they did NOT receive their Sinnoh Stones after completing a week of research, while others still did. This has led the community to believe that the stones are not guaranteed, but part of a larger reward pool.
Some users suspect that the guaranteed Sinnoh Stone rewards were only for the duration of the egg-hatching event. Others believe that this is a technical error on Niantic’s part, which will be resolved with awareness.
Niantic has not commented at this time.