Seems like mcpitanlib-2.3.9-1.21-fabric broke compatibility again.

https://pastebin.com/qpNtPEZ5

uploaded the latest MCPitanLib.

Same here, Fabric 1.21 server with latest fabric version.

[08:37:30] [Server thread/INFO]: Fly0ver joined the game
[08:37:30] [Server thread/ERROR]: Couldn't place player in world
java.lang.NullPointerException: Cannot invoke "net.minecraft.class_9139.encode(Object, Object)" because "codec" is null
at dev.architectury.impl.NetworkAggregator.collectPackets(NetworkAggregator.java:146) ~[architectury-13.0.6-fabric.jar:?]
at dev.architectury.networking.NetworkManager.collectPackets(NetworkManager.java:137) ~[architectury-13.0.6-fabric.jar:?]
at dev.architectury.networking.NetworkManager.sendToPlayer(NetworkManager.java:157) ~[architectury-13.0.6-fabric.jar:?]
at net.pitan76.mcpitanlib.api.network.ServerNetworking.send(ServerNetworking.java:31) ~[mcpitanlib-2.4.0-1.21-fabric.jar:?]
at net.pitan76.itemalchemy.EMCManager.syncS2C_emc_map(EMCManager.java:307) ~[itemalchemy-0.9.1.jar:?]
at net.pitan76.itemalchemy.ItemAlchemy.lambda$init$0(ItemAlchemy.java:56) ~[itemalchemy-0.9.1.jar:?]
at java.base/java.lang.invoke.MethodHandle.invokeWithArguments(MethodHandle.java:733) ~[?:?]
at dev.architectury.event.EventFactory.invokeMethod(EventFactory.java:53) ~[architectury-13.0.6-fabric.jar:?]
at dev.architectury.event.EventFactory$1.handleInvocation(EventFactory.java:62) ~[architectury-13.0.6-fabric.jar:?]
at com.google.common.reflect.AbstractInvocationHandler.invoke(AbstractInvocationHandler.java:87) ~[guava-32.1.2-jre.jar:?]
at jdk.proxy2/jdk.proxy2.$Proxy203.join(Unknown Source) ~[?:?]
at net.minecraft.class_3324.handler$zgf000$architectury$placeNewPlayer(class_3324.java:2009) ~[server-intermediary.jar:?]
at net.minecraft.class_3324.method_14570(class_3324.java:288) ~[server-intermediary.jar:?]
at net.minecraft.class_8610.mixinextras$bridge$method_14570$45(class_8610.java) ~[server-intermediary.jar:?]
at net.minecraft.class_8610.wrapOperation$dhk000$polymer-networking$polymerNet$prePlayHandshakeHackfest(class_8610.java:1038) ~[server-intermediary.jar:?]
at net.minecraft.class_8610.method_52408(class_8610.java:152) ~[server-intermediary.jar:?]
at net.minecraft.class_8736.method_53043(class_8736.java:22) ~[server-intermediary.jar:?]
at net.minecraft.class_8736.method_11054(class_8736.java:8) ~[server-intermediary.jar:?]
at net.minecraft.class_2600.method_11072(class_2600.java:27) ~[server-intermediary.jar:?]
at net.minecraft.class_3738.run(class_3738.java:18) ~[server-intermediary.jar:?]
at net.minecraft.class_1255.method_18859(class_1255.java:162) ~[server-intermediary.jar:?]
at net.minecraft.class_4093.method_18859(class_4093.java:23) ~[server-intermediary.jar:?]
at net.minecraft.server.MinecraftServer.method_24306(MinecraftServer.java:864) ~[server-intermediary.jar:?]
at net.minecraft.server.MinecraftServer.method_18859(MinecraftServer.java:173) ~[server-intermediary.jar:?]
at net.minecraft.class_1255.method_16075(class_1255.java:136) ~[server-intermediary.jar:?]
at net.minecraft.server.MinecraftServer.method_20415(MinecraftServer.java:846) ~[server-intermediary.jar:?]
at net.minecraft.server.MinecraftServer.method_16075(MinecraftServer.java:840) ~[server-intermediary.jar:?]
at net.minecraft.class_1255.method_18857(class_1255.java:145) ~[server-intermediary.jar:?]
at net.minecraft.server.MinecraftServer.method_18857(MinecraftServer.java:810) ~[server-intermediary.jar:?]
at net.minecraft.server.MinecraftServer.method_16208(MinecraftServer.java:815) ~[server-intermediary.jar:?]
at net.minecraft.server.MinecraftServer.method_29741(MinecraftServer.java:702) ~[server-intermediary.jar:?]
at net.minecraft.server.MinecraftServer.method_29739(MinecraftServer.java:281) ~[server-intermediary.jar:?]
at java.base/java.lang.Thread.run(Thread.java:1583) [?:?]
[08:37:30] [Server thread/INFO]: Fly0ver lost connection: Invalid player data
[08:37:30] [Server thread/INFO]: Fly0ver left the game