When I installed both MythicDungeons and ProtocolLib on the server, an error occurred and the player couldn't find the server. These two are good resources, hope to be able to use at the same time. My MC version is 1.17.1.
[14:36:43] [Netty Server IO #0/WARN]: An exceptionCaught() event was fired, and it reached at the tail of the pipeline. It usually means the last handler in the pipeline did not handle the exception. java.lang.IllegalStateException: zip file closed at java.util.zip.ZipFile.ensureOpen(ZipFile.java:831) ~[?:?] at java.util.zip.ZipFile.getEntry(ZipFile.java:330) ~[?:?] at java.util.jar.JarFile.getEntry(JarFile.java:518) ~[?:?] at java.util.jar.JarFile.getJarEntry(JarFile.java:473) ~[?:?] at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:159) ~[spigot-1.17.1.jar:3284a-Spigot-3892929-0ab8487] at java.lang.ClassLoader.loadClass(ClassLoader.java:587) ~[?:?] at org.bukkit.plugin.java.PluginClassLoader.loadClass0(PluginClassLoader.java:104) ~[spigot-1.17.1.jar:3284a-Spigot-3892929-0ab8487] at org.bukkit.plugin.java.PluginClassLoader.loadClass(PluginClassLoader.java:99) ~[spigot-1.17.1.jar:3284a-Spigot-3892929-0ab8487] at java.lang.ClassLoader.loadClass(ClassLoader.java:520) ~[?:?] at net.playavalon.mythicdungeons.packetevents.impl.injector.connection.ServerChannelHandler.channelRead(ServerChannelHandler.java:64) ~[?:?] at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362) [spigot-1.17.1.jar:3284a-Spigot-3892929-0ab8487] at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348) [spigot-1.17.1.jar:3284a-Spigot-3892929-0ab8487] at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:340) [spigot-1.17.1.jar:3284a-Spigot-3892929-0ab8487] at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1434) [spigot-1.17.1.jar:3284a-Spigot-3892929-0ab8487] at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362) [spigot-1.17.1.jar:3284a-Spigot-3892929-0ab8487] at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348) [spigot-1.17.1.jar:3284a-Spigot-3892929-0ab8487] at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:965) [spigot-1.17.1.jar:3284a-Spigot-3892929-0ab8487] at io.netty.channel.nio.AbstractNioMessageChannel$NioMessageUnsafe.read(AbstractNioMessageChannel.java:93) [spigot-1.17.1.jar:3284a-Spigot-3892929-0ab8487] at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:647) [spigot-1.17.1.jar:3284a-Spigot-3892929-0ab8487] at io.netty.channel.nio.NioEventLoop.processSelectedKeysPlain(NioEventLoop.java:547) [spigot-1.17.1.jar:3284a-Spigot-3892929-0ab8487] at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:501) [spigot-1.17.1.jar:3284a-Spigot-3892929-0ab8487] at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:461) [spigot-1.17.1.jar:3284a-Spigot-3892929-0ab8487] at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:884) [spigot-1.17.1.jar:3284a-Spigot-3892929-0ab8487] at java.lang.Thread.run(Thread.java:833) [?:?]