Log:
[14:04:51] [Server thread/INFO]: [Citizens] Enabling Citizens v2.0.38-SNAPSHOT (build 3766)
[14:04:51] [Server thread/INFO]: [Citizens] Using mojmapped server, avoiding server package checks
[14:04:51] [Server thread/ERROR]: [Citizens] Could not fetch NMS field bT: [[bT.
[14:04:51] [Server thread/ERROR]: [Citizens] Could not fetch NMS field bT: [[null.
[14:04:51] [Server thread/ERROR]: Error occurred while enabling Citizens v2.0.38-SNAPSHOT (build 3766) (Is it up to date?)
java.lang.NoClassDefFoundError: org/bukkit/craftbukkit/v1_21_R4/boss/CraftBossBar
	at Citizens-2.0.38-b3766.jar/net.citizensnpcs.nms.v1_21_R4.util.NMSImpl.<clinit>(NMSImpl.java:2742) ~[Citizens-2.0.38-b3766.jar:?]
	at java.base/java.lang.Class.forName0(Native Method) ~[?:?]
	at java.base/java.lang.Class.forName(Class.java:534) ~[?:?]
	at java.base/java.lang.Class.forName(Class.java:513) ~[?:?]
	at io.papermc.reflectionrewriter.runtime.AbstractDefaultRulesReflectionProxy.forName(AbstractDefaultRulesReflectionProxy.java:68) ~[reflection-rewriter-runtime-0.0.3.jar:?]
	at io.papermc.paper.pluginremap.reflect.PaperReflectionHolder.forName(Unknown Source) ~[paper-1.21.4.jar:1.21.4-221-c467df9]
	at Citizens-2.0.38-b3766.jar/net.citizensnpcs.api.util.SpigotUtil.lambda$getMinecraftPackage$1(SpigotUtil.java:175) ~[Citizens-2.0.38-b3766.jar:?]
	at Citizens-2.0.38-b3766.jar/net.citizensnpcs.api.util.SpigotUtil.getMinecraftPackage(SpigotUtil.java:180) ~[Citizens-2.0.38-b3766.jar:?]
	at Citizens-2.0.38-b3766.jar/net.citizensnpcs.Citizens.onEnable(Citizens.java:326) ~[Citizens-2.0.38-b3766.jar:?]
	at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:280) ~[paper-api-1.21.4-R0.1-SNAPSHOT.jar:?]
	at io.papermc.paper.plugin.manager.PaperPluginInstanceManager.enablePlugin(PaperPluginInstanceManager.java:202) ~[paper-1.21.4.jar:1.21.4-221-c467df9]
	at io.papermc.paper.plugin.manager.PaperPluginManagerImpl.enablePlugin(PaperPluginManagerImpl.java:109) ~[paper-1.21.4.jar:1.21.4-221-c467df9]
	at org.bukkit.plugin.SimplePluginManager.enablePlugin(SimplePluginManager.java:520) ~[paper-api-1.21.4-R0.1-SNAPSHOT.jar:?]
	at org.bukkit.craftbukkit.CraftServer.enablePlugin(CraftServer.java:657) ~[paper-1.21.4.jar:1.21.4-221-c467df9]
	at org.bukkit.craftbukkit.CraftServer.enablePlugins(CraftServer.java:606) ~[paper-1.21.4.jar:1.21.4-221-c467df9]
	at net.minecraft.server.MinecraftServer.loadWorld0(MinecraftServer.java:743) ~[paper-1.21.4.jar:1.21.4-221-c467df9]
	at net.minecraft.server.MinecraftServer.loadLevel(MinecraftServer.java:488) ~[paper-1.21.4.jar:1.21.4-221-c467df9]
	at net.minecraft.server.dedicated.DedicatedServer.initServer(DedicatedServer.java:322) ~[paper-1.21.4.jar:1.21.4-221-c467df9]
	at net.minecraft.server.MinecraftServer.runServer(MinecraftServer.java:1163) ~[paper-1.21.4.jar:1.21.4-221-c467df9]
	at net.minecraft.server.MinecraftServer.lambda$spin$2(MinecraftServer.java:310) ~[paper-1.21.4.jar:1.21.4-221-c467df9]
	at java.base/java.lang.Thread.run(Thread.java:1583) ~[?:?]
Caused by: java.lang.ClassNotFoundException: org.bukkit.craftbukkit.v1_21_R4.boss.CraftBossBar
	at org.bukkit.plugin.java.PluginClassLoader.loadClass0(PluginClassLoader.java:197) ~[paper-api-1.21.4-R0.1-SNAPSHOT.jar:?]
	at org.bukkit.plugin.java.PluginClassLoader.loadClass(PluginClassLoader.java:164) ~[paper-api-1.21.4-R0.1-SNAPSHOT.jar:?]
	at java.base/java.lang.ClassLoader.loadClass(ClassLoader.java:526) ~[?:?]
	... 21 more
[14:04:51] [Server thread/INFO]: [Citizens] Disabling Citizens v2.0.38-SNAPSHOT (build 3766)