Could not enable extension ArenaRegen-1.0.5.jar!

[Waxime64]

Impossibile to load ArenaRegen with Mohist and Duel didn't detect Victory
2021-06-03.log

Duels-3.4.1.jar and Duels-3.4.2-SNAPSHOT.jar
ArenaRegen-1.0.5.jar
mohist-1.16.5-619-server.jar

Plugins:
AdvancedTeleport-Bukkit-v5.4.7+DEV_15.jar
Citizens-2.0.27-b2316.jar
Duels-3.4.1.jar or Duels-3.4.2-SNAPSHOT.jar (I test both)
Vault.jar
worldedit-bukkit-7.2.5-dist.jar
worldguard-bukkit-7.0.4.jar

[21-06-03 20:28:55] [INFO] [DEBUG] Starting load of ExtensionManager at 1622766535346
[21-06-03 20:28:55] [SEVERE] ExtensionManager: Could not enable extension ArenaRegen-1.0.5.jar!
java.lang.NoClassDefFoundError: net/minecraft/server/v1_16_R3/Packet
at java.base/java.lang.Class.forName0(Native Method)
at java.base/java.lang.Class.forName(Unknown Source)
at me.realized.de.arenaregen.ArenaRegen.onEnable(ArenaRegen.java:44)
at me.realized.duels.api.extension.DuelsExtension.setEnabled(DuelsExtension.java:74)
at me.realized.duels.extension.ExtensionManager.handleLoad(ExtensionManager.java:83)
at me.realized.duels.DuelsPlugin.load(DuelsPlugin.java:253)
at me.realized.duels.DuelsPlugin.onEnable(DuelsPlugin.java:179)
at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:263)
at org.bukkit.plugin.java.JavaPluginLoader.enablePlugin(JavaPluginLoader.java:336)
at org.bukkit.plugin.SimplePluginManager.enablePlugin(SimplePluginManager.java:479)
at org.bukkit.craftbukkit.v1_16_R3.CraftServer.enablePlugin(CraftServer.java:490)
at org.bukkit.craftbukkit.v1_16_R3.CraftServer.enablePlugins(CraftServer.java:404)
at net.minecraft.server.MinecraftServer.func_240787_a_(MinecraftServer.java:431)
at net.minecraft.server.MinecraftServer.func_240800_l__(MinecraftServer.java:350)
at net.minecraft.server.dedicated.DedicatedServer.func_71197_b(DedicatedServer.java:217)
at net.minecraft.server.MinecraftServer.func_240802_v_(MinecraftServer.java:721)
at net.minecraft.server.MinecraftServer.func_240783_a_(MinecraftServer.java:270)
at java.base/java.lang.Thread.run(Unknown Source)
[21-06-03 20:28:55] [INFO] [DEBUG] ExtensionManager has been loaded. (took 108ms)