Could not load 'plugins\voicechat-bukkit-2.4.27 (4).jar' in folder 'plugins'

org.bukkit.plugin.InvalidPluginException: main class `de.maxhenkel.voicechat.Voicechat' does not extend JavaPlugin

        at org.bukkit.plugin.java.PluginClassLoader.<init>(PluginClassLoader.java:92) ~[forge:?]

        at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:144) ~[forge:?]

        at org.bukkit.plugin.SimplePluginManager.loadPlugin(SimplePluginManager.java:393) ~[forge:?]

        at org.bukkit.plugin.SimplePluginManager.loadPlugins(SimplePluginManager.java:301) ~[forge:?]

        at org.bukkit.craftbukkit.v1_16_R3.CraftServer.loadPlugins(CraftServer.java:389) ~[forge:7e29f765-296df566-9fb885e8]

        at net.minecraft.server.dedicated.DedicatedServer.func_71197_b(DedicatedServer.java:218) ~[?:?]

        at net.minecraft.server.MinecraftServer.func_240802_v_(MinecraftServer.java:768) ~[?:?]

        at net.minecraft.server.MinecraftServer.func_240783_a_(MinecraftServer.java:267) ~[?:?]

        at java.lang.Thread.run(Thread.java:1583) ~[?:?]

Caused by: java.lang.ClassCastException: class de.maxhenkel.voicechat.Voicechat

        at java.lang.Class.asSubclass(Class.java:4102) ~[?:?]

        at org.bukkit.plugin.java.PluginClassLoader.<init>(PluginClassLoader.java:90) ~[forge:?]

        ... 8 more

라고 뜨는데 모드랑 플러그인 다 했는데도 안되네요..

포트를 꼭 바꿔야 하나요?

그럼 어떻게 바꾸나요?