Error

[09:59:25 INFO]: [skDragon] Enabling skDragon v0.15
[09:59:25 ERROR]: Error occurred while enabling skDragon v0.15 (Is it up to date?)
java.lang.NoClassDefFoundError: ch/njol/skript/Skript
        at ud.skript.sashie.skDragonCore.onEnable(skDragonCore.java:100) ~[?:?]
        at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:264) ~[patched_1.12.2.jar:git-Paper-1618]
        at org.bukkit.plugin.java.JavaPluginLoader.enablePlugin(JavaPluginLoader.java:316) ~[patched_1.12.2.jar:git-Paper-1618]
        at org.bukkit.plugin.SimplePluginManager.enablePlugin(SimplePluginManager.java:405) ~[patched_1.12.2.jar:git-Paper-1618]
        at org.bukkit.craftbukkit.v1_12_R1.CraftServer.enablePlugin(CraftServer.java:395) ~[patched_1.12.2.jar:git-Paper-1618]
        at org.bukkit.craftbukkit.v1_12_R1.CraftServer.enablePlugins(CraftServer.java:344) ~[patched_1.12.2.jar:git-Paper-1618]
        at net.minecraft.server.v1_12_R1.MinecraftServer.t(MinecraftServer.java:442) ~[patched_1.12.2.jar:git-Paper-1618]
        at net.minecraft.server.v1_12_R1.MinecraftServer.l(MinecraftServer.java:403) ~[patched_1.12.2.jar:git-Paper-1618]
        at net.minecraft.server.v1_12_R1.MinecraftServer.a(MinecraftServer.java:341) ~[patched_1.12.2.jar:git-Paper-1618]
        at net.minecraft.server.v1_12_R1.DedicatedServer.init(DedicatedServer.java:289) ~[patched_1.12.2.jar:git-Paper-1618]
        at net.minecraft.server.v1_12_R1.MinecraftServer.run(MinecraftServer.java:616) ~[patched_1.12.2.jar:git-Paper-1618]
        at java.lang.Thread.run(Unknown Source) [?:1.8.0_211]
Caused by: java.lang.ClassNotFoundException: ch.njol.skript.Skript
        at java.net.URLClassLoader.findClass(Unknown Source) ~[?:1.8.0_211]
        at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:156) ~[patched_1.12.2.jar:git-Paper-1618]
        at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:104) ~[patched_1.12.2.jar:git-Paper-1618]
        at java.lang.ClassLoader.loadClass(Unknown Source) ~[?:1.8.0_211]
        at java.lang.ClassLoader.loadClass(Unknown Source) ~[?:1.8.0_211]
        ... 12 more