Sentinel plugin throws NoClassDefFoundError.

[Mineprank]

[02:41:10] [Server thread/WARN]: Entity threw exception at world:-325.35663359121673,82.0,216.06023692529564
[02:41:10] [Server thread/WARN]: java.lang.NoClassDefFoundError: com/palmergames/bukkit/towny/object/TownyUniverse
[02:41:10] [Server thread/WARN]: at org.mcmonkey.sentinel.integration.SentinelTowny.isTarget(SentinelTowny.java:51)
[02:41:10] [Server thread/WARN]: at org.mcmonkey.sentinel.targeting.SentinelTargetList.isTargetNoCache(SentinelTargetList.java:127)
[02:41:10] [Server thread/WARN]: at org.mcmonkey.sentinel.targeting.SentinelTargetList.isTarget(SentinelTargetList.java:72)
[02:41:10] [Server thread/WARN]: at org.mcmonkey.sentinel.targeting.SentinelTargetingHelper.isTargeted(SentinelTargetingHelper.java:215)
[02:41:10] [Server thread/WARN]: at org.mcmonkey.sentinel.targeting.SentinelTargetingHelper.shouldTarget(SentinelTargetingHelper.java:50)
[02:41:10] [Server thread/WARN]: at org.mcmonkey.sentinel.targeting.SentinelTargetingHelper.findBestTarget(SentinelTargetingHelper.java:422)
[02:41:10] [Server thread/WARN]: at org.mcmonkey.sentinel.SentinelTrait.runUpdate(SentinelTrait.java:1362)
[02:41:10] [Server thread/WARN]: at org.mcmonkey.sentinel.SentinelTrait.run(SentinelTrait.java:1588)
[02:41:10] [Server thread/WARN]: at net.citizensnpcs.api.npc.AbstractNPC.update(AbstractNPC.java:480)
[02:41:10] [Server thread/WARN]: at net.citizensnpcs.npc.CitizensNPC.update(CitizensNPC.java:350)
[02:41:10] [Server thread/WARN]: at net.citizensnpcs.nms.v1_16_R3.entity.EntityHumanNPC.tick(EntityHumanNPC.java:463)
[02:41:10] [Server thread/WARN]: at net.minecraft.server.v1_16_R3.WorldServer.entityJoinedWorld(WorldServer.java:846)
[02:41:10] [Server thread/WARN]: at net.minecraft.server.v1_16_R3.World.a(World.java:886)
[02:41:10] [Server thread/WARN]: at net.minecraft.server.v1_16_R3.WorldServer.doTick(WorldServer.java:531)
[02:41:10] [Server thread/WARN]: at net.minecraft.server.v1_16_R3.MinecraftServer.b(MinecraftServer.java:1364)
[02:41:10] [Server thread/WARN]: at net.minecraft.server.v1_16_R3.DedicatedServer.b(DedicatedServer.java:379)
[02:41:10] [Server thread/WARN]: at net.minecraft.server.v1_16_R3.MinecraftServer.a(MinecraftServer.java:1216)
[02:41:10] [Server thread/WARN]: at net.minecraft.server.v1_16_R3.MinecraftServer.w(MinecraftServer.java:1004)
[02:41:10] [Server thread/WARN]: at net.minecraft.server.v1_16_R3.MinecraftServer.lambda$a$0(MinecraftServer.java:177)
[02:41:10] [Server thread/WARN]: at java.lang.Thread.run(Unknown Source)

[LlmDl]

That plugin is using the old API which was deprecated in 2019 and removed recently. The plugin will need to update to our new API.