Hi, this is the error:

[18:00:51] [Server thread/INFO]: [ProtocolLib] Loading server plugin ProtocolLib v5.1.0
[18:00:51] [Server thread/WARN]: [ProtocolLib] Version (MC: 1.20.2) has not yet been tested! Proceed with caution.
[18:00:51] [Server thread/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:310)
at net.minecraft.server.MinecraftServer.w(MinecraftServer.java:1102)
at net.minecraft.server.MinecraftServer.lambda$spin$0(MinecraftServer.java:320)
at java.base/java.lang.Thread.run(Thread.java:842)
Dump:
Parameters:
[NULL]
Sender:
com.comphenix.protocol.ProtocolLib@273c9135[
statistics=
packetTask=
tickCounter=0
configExpectedMod=-1
updater=com.comphenix.protocol.updater.SpigotUpdater@426c32a
redirectHandler=
scheduler=com.comphenix.protocol.scheduler.DefaultScheduler@72267999
commandProtocol=
commandPacket=
commandFilter=
packetLogging=
skipDisable=false
isEnabled=false
loader=io.papermc.paper.plugin.manager.DummyBukkitPluginLoader@6e3bdead
server=CraftServer{serverName=Purpur,serverVersion=git-Purpur-2087,minecraftVersion=1.20.2}
file=plugins\ProtocolLib.jar
description=org.bukkit.plugin.PluginDescriptionFile@1f40e676
pluginMeta=org.bukkit.plugin.PluginDescriptionFile@1f40e676
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@6e15dd60
]
Version:
ProtocolLib v5.1.0
Java Version:
17.0.9
Server:
git-Purpur-2087 (MC: 1.20.2)

Same error,

[00:15:52] [Server thread/INFO]: [ProtocolLib] Loading server plugin ProtocolLib v5.1.0
[00:15:52] [Server thread/WARN]: [ProtocolLib] Version (MC: 1.20.2) has not yet been tested! Proceed with caution.
[00:15:55] [Server thread/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:310)
at net.minecraft.server.MinecraftServer.w(MinecraftServer.java:1102)
at net.minecraft.server.MinecraftServer.lambda$spin$0(MinecraftServer.java:320)
at java.base/java.lang.Thread.run(Thread.java:840)
Dump:
Parameters:
[NULL]
Sender:
com.comphenix.protocol.ProtocolLib@31e3c935[
statistics=
packetTask=
tickCounter=0
configExpectedMod=-1
updater=com.comphenix.protocol.updater.SpigotUpdater@48c2d8fa
redirectHandler=
scheduler=com.comphenix.protocol.scheduler.DefaultScheduler@26960c83
commandProtocol=
commandPacket=
commandFilter=
packetLogging=
skipDisable=false
isEnabled=false
loader=io.papermc.paper.plugin.manager.DummyBukkitPluginLoader@62155fb3
server=CraftServer{serverName=Purpur,serverVersion=git-Purpur-2082,minecraftVersion=1.20.2}
file=plugins/ProtocolLib.jar
description=org.bukkit.plugin.PluginDescriptionFile@13cb9ce5
pluginMeta=org.bukkit.plugin.PluginDescriptionFile@13cb9ce5
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@4d8f57da
]
Version:
ProtocolLib v5.1.0
Java Version:
17.0.9
Server:
git-Purpur-2082 (MC: 1.20.2)

Try to use dev build of ProtocolLib v5.1.1 from here:
[1.8-1.19.4]: https://ci.dmulloy2.net/job/
[1.20.*+]: https://ci.dmulloy2.net/job/ProtocolLib/669/

Notice for 1.20 and 1.20.1 users:
Please, use 1.20.2 to confirm your issue with ProtocolLib.

Why not the last build for 1.20.2?
Last build (673) have critical issue at this moment; #2601

If the problem persists, provide more information about your problem using this form:

• This issue is not solved in a development build

Describe the bug
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To Reproduce
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4. See error

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Version Info
Provide your ProtocolLib install info with /protocol dump through pastebin.

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