Development Assistance Custom NPCs

I just downloaded and added Citizens version 1.7.4 (My server version) to my build path and to my server plugins. Any ideas what is wrong with this? Am I using an outdated version or something? My build path is using my plugin so it can't be a different version and I have depended it in my plugin#yml. I got this error...

Code:

org.bukkit.command.CommandException: Unhandled exception executing command 'p' i
n plugin PotionPVP v1.0
        at org.bukkit.command.PluginCommand.execute(PluginCommand.java:46) ~[spi
got.jar:git-Spigot-1571]
        at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:18
1) ~[spigot.jar:git-Spigot-1571]
        at org.bukkit.craftbukkit.v1_7_R4.CraftServer.dispatchCommand(CraftServe
r.java:767) ~[spigot.jar:git-Spigot-1571]
        at net.minecraft.server.v1_7_R4.PlayerConnection.handleCommand(PlayerCon
nection.java:1010) [spigot.jar:git-Spigot-1571]
        at net.minecraft.server.v1_7_R4.PlayerConnection.a(PlayerConnection.java
:847) [spigot.jar:git-Spigot-1571]
        at net.minecraft.server.v1_7_R4.PacketPlayInChat.a(PacketPlayInChat.java
:28) [spigot.jar:git-Spigot-1571]
        at net.minecraft.server.v1_7_R4.PacketPlayInChat.handle(PacketPlayInChat
.java:65) [spigot.jar:git-Spigot-1571]
        at net.minecraft.server.v1_7_R4.NetworkManager.a(NetworkManager.java:184
) [spigot.jar:git-Spigot-1571]
        at net.minecraft.server.v1_7_R4.ServerConnection.c(ServerConnection.java
:81) [spigot.jar:git-Spigot-1571]
        at net.minecraft.server.v1_7_R4.MinecraftServer.v(MinecraftServer.java:7
31) [spigot.jar:git-Spigot-1571]
        at net.minecraft.server.v1_7_R4.DedicatedServer.v(DedicatedServer.java:2
89) [spigot.jar:git-Spigot-1571]
        at net.minecraft.server.v1_7_R4.MinecraftServer.u(MinecraftServer.java:5
84) [spigot.jar:git-Spigot-1571]
        at net.minecraft.server.v1_7_R4.MinecraftServer.run(MinecraftServer.java
:490) [spigot.jar:git-Spigot-1571]
        at net.minecraft.server.v1_7_R4.ThreadServerApplication.run(SourceFile:6
28) [spigot.jar:git-Spigot-1571]
Caused by: java.lang.NoClassDefFoundError: net/citizensnpcs/api/CitizensAPI
        at minecraft.pot.serverbot.BotManager.SpawnNPC(BotManager.java:16) ~[?:?
]
        at minecraft.pot.commands.Ping.onCommand(Ping.java:26) ~[?:?]
        at org.bukkit.command.PluginCommand.execute(PluginCommand.java:44) ~[spi
got.jar:git-Spigot-1571]
        ... 13 more
Caused by: java.lang.ClassNotFoundException: net.citizensnpcs.api.CitizensAPI
        at java.net.URLClassLoader$1.run(Unknown Source) ~[?:1.8.0_25]
        at java.net.URLClassLoader$1.run(Unknown Source) ~[?:1.8.0_25]
        at java.security.AccessController.doPrivileged(Native Method) ~[?:1.8.0_
25]
        at java.net.URLClassLoader.findClass(Unknown Source) ~[?:1.8.0_25]
        at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.
java:98) ~[spigot.jar:git-Spigot-1571]
        at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.
java:83) ~[spigot.jar:git-Spigot-1571]
        at java.lang.ClassLoader.loadClass(Unknown Source) ~[?:1.8.0_25]
        at java.lang.ClassLoader.loadClass(Unknown Source) ~[?:1.8.0_25]
        at minecraft.pot.serverbot.BotManager.SpawnNPC(BotManager.java:16) ~[?:?
]
        at minecraft.pot.commands.Ping.onCommand(Ping.java:26) ~[?:?]
        at org.bukkit.command.PluginCommand.execute(PluginCommand.java:44) ~[spi
got.jar:git-Spigot-1571]
        ... 13 more

This is my current code...

Code:

    public void SpawnNPC(String name, Location l, Entity e) {
        NPCRegistry registry = CitizensAPI.getNPCRegistry(); // Line 16
        NPC npc = registry.createNPC(EntityType.PLAYER, name);
        npc.spawn(l);
        npc.getNavigator().setTarget(e, true);
    }

EDIT: In case you're wondering, this post recently got moved to another thread but I don't really understand why as I'm using an API to develop my own plugin. This is the reason why it was under Plugin Development in the first place. So I re-posted and marked the other one as solved.

 

Is the API installed in the server? Is it the same version as the one you build against?