Server error with globalmanager?

[Mineshaft87]

Hey guys i'm trying to get Essentials global manager onto my server so i can make ranks etc. I added the plugin i did /manuadd (name) admin... and it came up with this error...

22:03:54 [sEVERE] null

org.bukkit.command.CommandException: Unhandled exception executing command 'manu

add' in plugin GroupManager v2.0 (2.10.1) (Phoenix)

at org.bukkit.command.PluginCommand.execute(PluginCommand.java:42)

at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:16

6)

at forge.bukkit.ForgeCommandMap.dispatch(ForgeCommandMap.java:55)

at org.bukkit.craftbukkit.CraftServer.dispatchCommand(CraftServer.java:4

97)

at net.minecraft.server.NetServerHandler.handleCommand(NetServerHandler.

java:843)

at net.minecraft.server.NetServerHandler.chat(NetServerHandler.java:799)

at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:781)

at net.minecraft.server.Packet3Chat.handle(Packet3Chat.java:34)

at net.minecraft.server.NetworkManager.b(NetworkManager.java:234)

at net.minecraft.server.NetServerHandler.a(NetServerHandler.java:119)

at net.minecraft.server.NetworkListenThread.a(NetworkListenThread.java:8

3)

at net.minecraft.server.MinecraftServer.w(MinecraftServer.java:579)

at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:467)

at net.minecraft.server.ThreadServerApplication.run(SourceFile:492)

Caused by: java.lang.NoClassDefFoundError: org/bukkit/command/BlockCommandSender

at org.anjocaido.groupmanager.GroupManager.onCommand(GroupManager.java:3

94)

at org.bukkit.command.PluginCommand.execute(PluginCommand.java:40)

... 13 more

Caused by: java.lang.ClassNotFoundException: org.bukkit.command.BlockCommandSend

er

at java.net.URLClassLoader$1.run(Unknown Source)

at java.net.URLClassLoader$1.run(Unknown Source)

at java.security.AccessController.doPrivileged(Native Method)

at java.net.URLClassLoader.findClass(Unknown Source)

at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.

java:41)

at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.

java:29)

at java.lang.ClassLoader.loadClass(Unknown Source)

at java.lang.ClassLoader.loadClass(Unknown Source)

... 15 more

I had a good read through it and am pretty sure it's nothing to do with the plugin being out of date. Would be very grateful if someone helped me out here because global manager is pretty essentials to any server!

p.s I'm running Tekkit classic

Thanks,

Mineshaft87