Stack Trace:
java.lang.ExceptionInInitializerError
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:203)
at org.bukkit.craftbukkit.v1_16_R3.CraftServer.loadPlugins(CraftServer.java:386)
at net.minecraft.server.dedicated.DedicatedServer.func_71197_b(DedicatedServer.java:244)
at net.minecraft.server.MinecraftServer.func_240802_v_(MinecraftServer.java:826)
at net.minecraft.server.MinecraftServer.func_240783_a_(MinecraftServer.java:286)
at java.base/java.lang.Thread.run(Thread.java:834)
Caused by: java.lang.RuntimeException: Unable to find network.EnumProtocol (EnumProtocol)
at com.comphenix.protocol.utility.MinecraftReflection.getMinecraftClass(MinecraftReflection.java:2143)
at com.comphenix.protocol.utility.MinecraftReflection.getEnumProtocolClass(MinecraftReflection.java:760)
at com.comphenix.protocol.injector.packet.PacketRegistry.(PacketRegistry.java:88)
... 9 more
Dump:
Parameters:
[NULL]
Sender:
com.comphenix.protocol.ProtocolLib@132c0dba[
statistics=
backgroundCompiler=
packetTask=-1
tickCounter=0
unhookTask=com.comphenix.protocol.injector.DelayedSingleTask@58a782af
configExpectedMod=-1
updater=com.comphenix.protocol.updater.SpigotUpdater@4a10b78d
redirectHandler=
commandProtocol=
commandPacket=
commandFilter=
packetLogging=
skipDisable=false
isEnabled=false
loader=org.bukkit.plugin.java.JavaPluginLoader@4ff37f0a
server=CraftServer{serverName=Magma,serverVersion=git-Magma-1.16.5-36.2.8-5faa5ec-DEV,minecraftVersion=1.16.5}
file=plugins/protocollib.jar
description=org.bukkit.plugin.PluginDescriptionFile@5817a55e
dataFolder=plugins/ProtocolLib
classLoader=org.bukkit.plugin.java.PluginClassLoader@e823a98
naggable=true
newConfig=YamlConfiguration[path='', root='YamlConfiguration']
configFile=plugins/ProtocolLib/config.yml
logger=org.bukkit.plugin.PluginLogger@43abebc5
]
Version:
ProtocolLib v4.7.0
Java Version:
11.0.10
Server:
git-Magma-1.16.5-36.2.8-5faa5ec-DEV (MC: 1.16.5)

These types of issues appear with non-standard servers, i.e. those not in the Paper/Spigot ecosystem. Unfortunately due to their wide variety, ProtocolLib cannot support all of them and sometimes these issues appear. You are welcome open a pull request to try to address it.