at net.minecraft.server.v1_16_R3.MinecraftServer.lambda$a$0(MinecraftServer.java:293)
    at net.minecraft.server.v1_16_R3.MinecraftServer$$Lambda$3146/0x000000005df38e08.run(Unknown Source)
    at java.base/java.lang.Thread.run(Thread.java:883)

Caused by: java.lang.IllegalAccessException: illegal setter on final field
at java.base/java.lang.invoke.MethodHandles$Lookup.findSetter(MethodHandles.java:1084)
at com.comphenix.protocol.reflect.accessors.MethodHandleHelper.getFieldAccessor(MethodHandleHelper.java:96)
... 14 more
Dump:
manager:
com.comphenix.protocol.injector.PacketFilterManager@ef90dc7b[
plugin=ProtocolLib v5.1.0
server=CraftServer{serverName=Purpur,serverVersion=git-Purpur-1171,minecraftVersion=1.16.5}
reporter=com.comphenix.protocol.ProtocolLib$1@861a4c1d
minecraftVersion=(MC: 1.16.5)
asyncFilterManager=com.comphenix.protocol.async.AsyncFilterManager@b62a6cb4
pluginVerifier=com.comphenix.protocol.injector.PluginVerifier@d8b9a837
inboundListeners=com.comphenix.protocol.injector.SortedPacketListenerList@b9aef31
outboundListeners=com.comphenix.protocol.injector.SortedPacketListenerList@1a1b893f
registeredListeners=[]
packetInjector=com.comphenix.protocol.injector.netty.manager.NetworkManagerPacketInjector@d6fc0d7a
playerInjectionHandler=com.comphenix.protocol.injector.netty.manager.NetworkManagerPlayerInjector@7a9390dc
networkManagerInjector=com.comphenix.protocol.injector.netty.manager.NetworkManagerInjector@a7becf0d
debug=false
closed=false
injected=true
]
Sender:
com.comphenix.protocol.ProtocolLib@9ec79703[
statistics=
packetTask=
tickCounter=0
configExpectedMod=-1
updater=com.comphenix.protocol.updater.SpigotUpdater@5495e887
redirectHandler=com.comphenix.protocol.ProtocolLib$2@9c248ffc
scheduler=com.comphenix.protocol.scheduler.DefaultScheduler@8b9bf94f
commandProtocol=com.comphenix.protocol.CommandProtocol@cf3eee50
commandPacket=com.comphenix.protocol.CommandPacket@a062d9
commandFilter=com.comphenix.protocol.CommandFilter@31d43d2b
packetLogging=com.comphenix.protocol.PacketLogging@bec8bd79
skipDisable=false
isEnabled=true
loader=org.bukkit.plugin.java.JavaPluginLoader@55d57a79
server=CraftServer{serverName=Purpur,serverVersion=git-Purpur-1171,minecraftVersion=1.16.5}
file=plugins/ProtocolLib.jar
description=org.bukkit.plugin.PluginDescriptionFile@bca30f77
dataFolder=plugins/ProtocolLib
classLoader=PluginClassLoader{plugin=ProtocolLib v5.1.0, pluginEnabled=true, url=plugins/ProtocolLib.jar}
naggable=true
newConfig=YamlConfiguration[path='', root='YamlConfiguration']
configFile=plugins/ProtocolLib/config.yml
logger=com.destroystokyo.paper.utils.PaperPluginLogger@13286410
]
Version:
ProtocolLib v5.1.0
Java Version:
16.0.2
Server:
git-Purpur-1171 (MC: 1.16.5)

[22:56:33 INFO]: [ProtocolLib] Disabling ProtocolLib v5.1.0

[10:05:34 ERROR]: [ProtocolLib] INTERNAL ERROR: Cannot load ProtocolLib.
If this problem hasn't already been reported, please open a ticket
at https://github.com/dmulloy2/ProtocolLib/issues with the following data:
Stack Trace:
java.lang.IllegalArgumentException: Unable to find a field that matches {modifiers=[required: 10000, banned: 1000], type={ type input instanceof interface java.util.Map }}
at ProtocolLib.jar//com.comphenix.protocol.reflect.FuzzyReflection.getField(FuzzyReflection.java:352)
at ProtocolLib.jar//com.comphenix.protocol.injector.packet.PacketRegistry.createNewRegister(PacketRegistry.java:188)
at ProtocolLib.jar//com.comphenix.protocol.injector.packet.PacketRegistry.initialize(PacketRegistry.java:292)
at ProtocolLib.jar//com.comphenix.protocol.injector.packet.PacketRegistry.getClientPacketTypes(PacketRegistry.java:327)
at ProtocolLib.jar//com.comphenix.protocol.injector.PacketFilterManager.(PacketFilterManager.java:120)
at ProtocolLib.jar//com.comphenix.protocol.injector.PacketFilterBuilder.build(PacketFilterBuilder.java:121)
at ProtocolLib.jar//com.comphenix.protocol.ProtocolLib.onLoad(ProtocolLib.java:183)
at io.papermc.paper.plugin.storage.ServerPluginProviderStorage.processProvided(ServerPluginProviderStorage.java:59)
at io.papermc.paper.plugin.storage.ServerPluginProviderStorage.processProvided(ServerPluginProviderStorage.java:18)
at io.papermc.paper.plugin.storage.SimpleProviderStorage.enter(SimpleProviderStorage.java:40)
at io.papermc.paper.plugin.entrypoint.LaunchEntryPointHandler.enter(LaunchEntryPointHandler.java:36)
at org.bukkit.craftbukkit.v1_20_R2.CraftServer.loadPlugins(CraftServer.java:526)
at net.minecraft.server.dedicated.DedicatedServer.e(DedicatedServer.java:307)
at net.minecraft.server.MinecraftServer.w(MinecraftServer.java:1100)
at net.minecraft.server.MinecraftServer.lambda$spin$0(MinecraftServer.java:318)
at java.base/java.lang.Thread.run(Thread.java:833)
Dump:
Parameters:
[NULL]
Sender:
com.comphenix.protocol.ProtocolLib@652afd57[
statistics=
packetTask=
tickCounter=0
configExpectedMod=-1
updater=com.comphenix.protocol.updater.SpigotUpdater@46b2a931
redirectHandler=
scheduler=com.comphenix.protocol.scheduler.DefaultScheduler@700af8d9
commandProtocol=
commandPacket=
commandFilter=
packetLogging=
skipDisable=false
isEnabled=false
loader=io.papermc.paper.plugin.manager.DummyBukkitPluginLoader@76097be
server=CraftServer{serverName=Purpur,serverVersion=git-Purpur-2074,minecraftVersion=1.20.2}
file=plugins/ProtocolLib.jar
description=org.bukkit.plugin.PluginDescriptionFile@663acee2
pluginMeta=org.bukkit.plugin.PluginDescriptionFile@663acee2
dataFolder=plugins/ProtocolLib
classLoader=PluginClassLoader{plugin=ProtocolLib v5.1.0, pluginEnabled=false, url=plugins/ProtocolLib.jar}
naggable=true
newConfig=YamlConfiguration[path='', root='YamlConfiguration']
configFile=plugins/ProtocolLib/config.yml
logger=com.destroystokyo.paper.utils.PaperPluginLogger@428f9c3f
]
Version:
ProtocolLib v5.1.0
Java Version:
17.0.8.1
Server:
git-Purpur-2074 (MC: 1.20.2)
[10:05:35 INFO]: [ProtocolLib] Enabling ProtocolLib v5.1.0
[10:05:35 ERROR]: ******************************************************
[10:05:35 ERROR]: *** ProtocolLib does not support plugin reloaders! ***
[10:05:35 ERROR]: *** Please use the built-in reload command! ***
[10:05:35 ERROR]: ******************************************************
[10:05:35 INFO]: [ProtocolLib] Disabling ProtocolLib v5.1.0

@mok3103 You need to use this development build https://ci.dmulloy2.net/job/ProtocolLib/669/ for Minecraft 1.20.2 support. ProtocolLib 5.1.0 only supports Minecraft 1.20.1