Make sure you're doing the following

• You're using the latest build for your server version
• This isn't an issue caused by another plugin
• You've checked for duplicate issues
• You didn't use /reload

Describe the question
A clear and concise description of what your question is.
I have downloaded the plugin ProtocolLib but the console just says:
18.02 18:32:31 [Server] Server thread/ERROR Could not load 'plugins/ProtocolLib.jar' in folder 'plugins'
18.02 18:32:31 [Server] INFO org.bukkit.plugin.InvalidPluginException: java.lang.IllegalArgumentException: Plugin already initialized!
18.02 18:32:31 [Server] INFO at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:139) ~[Spigot_Latest.jar:3013-Spigot-73fb609-0cd8f19]
18.02 18:32:31 [Server] INFO at org.bukkit.plugin.SimplePluginManager.loadPlugin(SimplePluginManager.java:394) ~[Spigot_Latest.jar:3013-Spigot-73fb609-0cd8f19]
18.02 18:32:31 [Server] INFO at org.bukkit.plugin.SimplePluginManager.loadPlugins(SimplePluginManager.java:301) ~[Spigot_Latest.jar:3013-Spigot-73fb609-0cd8f19]
18.02 18:32:31 [Server] INFO at org.bukkit.craftbukkit.v1_16_R3.CraftServer.loadPlugins(CraftServer.java:382) ~[Spigot_Latest.jar:3013-Spigot-73fb609-0cd8f19]
18.02 18:32:31 [Server] INFO at net.minecraft.server.v1_16_R3.DedicatedServer.init(DedicatedServer.java:185) ~[Spigot_Latest.jar:3013-Spigot-73fb609-0cd8f19]
18.02 18:32:31 [Server] INFO at net.minecraft.server.v1_16_R3.MinecraftServer.w(MinecraftServer.java:809) ~[Spigot_Latest.jar:3013-Spigot-73fb609-0cd8f19]
18.02 18:32:31 [Server] INFO at net.minecraft.server.v1_16_R3.MinecraftServer.lambda$0(MinecraftServer.java:164) ~[Spigot_Latest.jar:3013-Spigot-73fb609-0cd8f19]
18.02 18:32:31 [Server] INFO at java.lang.Thread.run(Thread.java:748) [?:1.8.0_211]
18.02 18:32:31 [Server] INFO Caused by: java.lang.IllegalArgumentException: Plugin already initialized!
18.02 18:32:31 [Server] INFO at org.bukkit.plugin.java.PluginClassLoader.initialize(PluginClassLoader.java:199) ~[Spigot_Latest.jar:3013-Spigot-73fb609-0cd8f19]
18.02 18:32:31 [Server] INFO at org.bukkit.plugin.java.JavaPlugin.(JavaPlugin.java:52) ~[Spigot_Latest.jar:3013-Spigot-73fb609-0cd8f19]
18.02 18:32:31 [Server] INFO at com.comphenix.protocol.ProtocolLib.(ProtocolLib.java:65) ~[?:?]
18.02 18:32:31 [Server] INFO at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[?:1.8.0_211]
18.02 18:32:31 [Server] INFO at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62) ~[?:1.8.0_211]
18.02 18:32:31 [Server] INFO at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[?:1.8.0_211]
18.02 18:32:31 [Server] INFO at java.lang.reflect.Constructor.newInstance(Constructor.java:423) ~[?:1.8.0_211]
18.02 18:32:31 [Server] INFO at java.lang.Class.newInstance(Class.java:442) ~[?:1.8.0_211]
18.02 18:32:31 [Server] INFO at org.bukkit.plugin.java.PluginClassLoader.(PluginClassLoader.java:76) ~[Spigot_Latest.jar:3013-Spigot-73fb609-0cd8f19]
18.02 18:32:31 [Server] INFO at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:135) ~[Spigot_Latest.jar:3013-Spigot-73fb609-0cd8f19]
18.02 18:32:31 [Server] INFO ... 7 more
18.02 18:32:31 [Server] INFO Caused by: java.lang.IllegalStateException: Initial initialization
18.02 18:32:31 [Server] INFO at org.bukkit.plugin.java.PluginClassLoader.initialize(PluginClassLoader.java:202) ~[Spigot_Latest.jar:3013-Spigot-73fb609-0cd8f19]
18.02 18:32:31 [Server] INFO at org.bukkit.plugin.java.JavaPlugin.(JavaPlugin.java:52) ~[Spigot_Latest.jar:3013-Spigot-73fb609-0cd8f19]
18.02 18:32:31 [Server] INFO at unet.Holograms.Main.(Main.java:27) ~[?:?]
18.02 18:32:31 [Server] INFO at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method) ~[?:1.8.0_211]
18.02 18:32:31 [Server] INFO at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62) ~[?:1.8.0_211]
18.02 18:32:31 [Server] INFO at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45) ~[?:1.8.0_211]
18.02 18:32:31 [Server] INFO at java.lang.reflect.Constructor.newInstance(Constructor.java:423) ~[?:1.8.0_211]
18.02 18:32:31 [Server] INFO at java.lang.Class.newInstance(Class.java:442) ~[?:1.8.0_211]
18.02 18:32:31 [Server] INFO at org.bukkit.plugin.java.PluginClassLoader.(PluginClassLoader.java:76) ~[Spigot_Latest.jar:3013-Spigot-73fb609-0cd8f19]
18.02 18:32:31 [Server] INFO at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:135) ~[Spigot_Latest.jar:3013-Spigot-73fb609-0cd8f19]
18.02 18:32:31 [Server] INFO ... 7 more

API method(s) used
List what API method(s) you're using
I do not know what that is.
Expected behavior
A clear and concise description of what you expected to happen.
I expected the plugin to work like normal and just pop up when I write /plugins
Code
If applicable, add relevant code from your project

Additional context
Add any other context about the problem here.
I am using Placeholder-API too
And I am using ProtocolLib for Interactivechat

[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.RuntimeException: Failed to find CraftBukkit class: entity.CraftPlayer
at com.comphenix.protocol.utility.MinecraftReflection.lambda$getCraftBukkitClass$0(MinecraftReflection.java:2014)
at java.util.Optional.orElseThrow(Optional.java:290)
at com.comphenix.protocol.utility.MinecraftReflection.getCraftBukkitClass(MinecraftReflection.java:2014)
at com.comphenix.protocol.utility.MinecraftReflection.getEntityPlayerClass(MinecraftReflection.java:588)
at com.comphenix.protocol.utility.MinecraftReflection.getPlayerConnectionClass(MinecraftReflection.java:1047)
at com.comphenix.protocol.utility.MinecraftReflection.getNetworkManagerClass(MinecraftReflection.java:1082)
at com.comphenix.protocol.utility.MinecraftReflection.getEnumProtocolClass(MinecraftReflection.java:758)
at com.comphenix.protocol.injector.netty.ProtocolRegistry.(ProtocolRegistry.java:58)
at com.comphenix.protocol.injector.netty.NettyProtocolRegistry.(NettyProtocolRegistry.java:43)
at com.comphenix.protocol.injector.packet.PacketRegistry.initialize(PacketRegistry.java:54)
at com.comphenix.protocol.injector.packet.PacketRegistry.getClientPacketTypes(PacketRegistry.java:112)
at com.comphenix.protocol.injector.PacketFilterManager.(PacketFilterManager.java:211)
at com.comphenix.protocol.injector.PacketFilterBuilder.buildInternal(PacketFilterBuilder.java:185)
at com.comphenix.protocol.injector.PacketFilterBuilder.build(PacketFilterBuilder.java:177)
at com.comphenix.protocol.ProtocolLib.onLoad(ProtocolLib.java:198)
at org.bukkit.craftbukkit.CraftServer.loadPlugins(CraftServer.java:375)
at net.minecraft.class_3176.handler$zza000$init(class_3176.java:741)
at net.minecraft.class_3176.method_3823(class_3176.java:155)
at net.minecraft.server.MinecraftServer.method_29741(MinecraftServer.java:645)
at net.minecraft.server.MinecraftServer.method_29739(MinecraftServer.java:257)
at java.lang.Thread.run(Thread.java:748)
Dump:
Parameters:
[NULL]
Sender:
com.comphenix.protocol.ProtocolLib@23ae5905[
statistics=
backgroundCompiler=
packetTask=-1
tickCounter=0
unhookTask=com.comphenix.protocol.injector.DelayedSingleTask@b464ea1
configExpectedMod=-1
updater=com.comphenix.protocol.updater.SpigotUpdater@35bdfc65
redirectHandler=
commandProtocol=
commandPacket=
commandFilter=
packetLogging=
skipDisable=false
isEnabled=false
loader=org.bukkit.plugin.java.JavaPluginLoader@3a80f012
server=CraftServer{serverName=CardboardPowered.org,serverVersion=git-Bukkit4Fabric-3cb2109,minecraftVersion=1.16.4}
file=plugins\ProtocolLib (7).jar
description=org.bukkit.plugin.PluginDescriptionFile@52bd98a7
dataFolder=plugins\ProtocolLib
classLoader=PluginClassLoader{plugin=ProtocolLib v4.6.0, pluginEnabled=false, url=plugins\ProtocolLib (7).jar}
naggable=true
newConfig=YamlConfiguration[path='', root='YamlConfiguration']
configFile=plugins\ProtocolLib\config.yml
logger=com.javazilla.bukkitfabric.BukkitLogger@35846934
]
Version:
ProtocolLib v4.6.0
Java Version:
1.8.0_281
Server:
git-Bukkit4Fabric-3cb2109 (MC: 1.16.4)

[18:57:52] [Server thread/INFO]: Enabling ProtocolLib v4.6.0
[18:57:52] [Server thread/INFO]: Disabling ProtocolLib v4.6.0

Looks like two separate issues but @apelsin222 it looks like you have two versions of PL in your plugin folder.

@ostinostin We don't currently support Bukkit4Fabric