Spigot and Paper have split up. The PlayerQuests community decided to choose Paper. I'm sorry Spigot friends.
This plugin will no longer work on Spigot as of 1.21.6 (v0.10.1 and above).
I don't have the resources to manage separate Spigot and Paper versions. It seems that writing it for Paper means it supports the biggest variety of servers, rather than Spigot which only supports the Spigot runtime. However, I'm happy to contribute back to a spigot version if it's led by another developer!