[15:21:10] [Server thread/INFO]: Kai_Hui issued server command: /class attr
[15:21:10] [Server thread/ERROR]: null
org.bukkit.command.CommandException: Unhandled exception executing 'class attr' in class
        at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:162) ~[Paper-1.12.2-b1618.jar:git-Paper-1618]
        at org.bukkit.craftbukkit.v1_12_R1.CraftServer.dispatchCommand(CraftServer.java:685) ~[Paper-1.12.2-b1618.jar:git-Paper-1618]
        at net.minecraft.server.v1_12_R1.PlayerConnection.handleCommand(PlayerConnection.java:1492) ~[Paper-1.12.2-b1618.jar:git-Paper-1618]
        at net.minecraft.server.v1_12_R1.PlayerConnection.a(PlayerConnection.java:1297) ~[Paper-1.12.2-b1618.jar:git-Paper-1618]
        at net.minecraft.server.v1_12_R1.PacketPlayInChat.a(PacketPlayInChat.java:45) ~[Paper-1.12.2-b1618.jar:git-Paper-1618]
        at net.minecraft.server.v1_12_R1.PacketPlayInChat.a(PacketPlayInChat.java:5) ~[Paper-1.12.2-b1618.jar:git-Paper-1618]
        at net.minecraft.server.v1_12_R1.PlayerConnectionUtils.lambda$ensureMainThread$0(PlayerConnectionUtils.java:14) ~[Paper-1.12.2-b1618.jar:git-Paper-1618]
        at java.util.concurrent.Executors$RunnableAdapter.call(Unknown Source) ~[?:1.8.0_311]
        at java.util.concurrent.FutureTask.run(Unknown Source) ~[?:1.8.0_311]
        at net.minecraft.server.v1_12_R1.SystemUtils.a(SourceFile:46) ~[Paper-1.12.2-b1618.jar:git-Paper-1618]
        at net.minecraft.server.v1_12_R1.MinecraftServer.D(MinecraftServer.java:850) ~[Paper-1.12.2-b1618.jar:git-Paper-1618]
        at net.minecraft.server.v1_12_R1.DedicatedServer.D(DedicatedServer.java:423) ~[Paper-1.12.2-b1618.jar:git-Paper-1618]
        at net.minecraft.server.v1_12_R1.MinecraftServer.C(MinecraftServer.java:774) ~[Paper-1.12.2-b1618.jar:git-Paper-1618]
        at net.minecraft.server.v1_12_R1.MinecraftServer.run(MinecraftServer.java:666) ~[Paper-1.12.2-b1618.jar:git-Paper-1618]
        at java.lang.Thread.run(Unknown Source) [?:1.8.0_311]
Caused by: java.lang.NullPointerException
        at com.sucy.skill.manager.AttributeManager$Attribute.filter(AttributeManager.java:295) ~[?:?]
        at com.sucy.skill.manager.AttributeManager$Attribute.getIcon(AttributeManager.java:269) ~[?:?]
        at com.sucy.skill.gui.tool.GUIPage.instance(GUIPage.java:154) ~[?:?]
        at com.sucy.skill.gui.tool.GUIData.show(GUIData.java:82) ~[?:?]
        at com.sucy.skill.api.player.PlayerData.openAttributeMenu(PlayerData.java:523) ~[?:?]
        at com.sucy.skill.cmd.CmdAttribute.execute(CmdAttribute.java:68) ~[?:?]
        at com.rit.sucy.commands.ConfigurableCommand.execute(ConfigurableCommand.java:550) ~[?:?]
        at com.rit.sucy.commands.ConfigurableCommand.execute(ConfigurableCommand.java:558) ~[?:?]
        at com.rit.sucy.commands.ConfigurableCommand.execute(ConfigurableCommand.java:516) ~[?:?]
        at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:152) ~[Paper-1.12.2-b1618.jar:git-Paper-1618]
        ... 14 more
这个是报错，完全打不开也用不了

换个版本试试

1.12我建议你使用这个版本
ProSkillAPI 枫溪版  增加了很多功能的 skillapi 1.12.2
https://www.mcbbs.net/thread-1385468-1-1.html
(出处: Minecraft(我的世界)中文论坛)
以及你在配置文件里启动了属性嘛？attributes-enabled: false改成true

换过没用

我用了喵技当技能界面，换插件不太方便 ，我启动了属性了