Compiled plugin (1.16.5) console error

[Varga-Levente]

[20:45:00] [Server thread/ERROR]: Error occurred while disabling Frequency v1.0 (Is it up to date?)
java.lang.NoClassDefFoundError: Could not initialize class xyz.elevated.frequency.Frequency
at xyz.elevated.frequency.FrequencyPlugin.onDisable(FrequencyPlugin.java:14) ~[?:?]
at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:265) ~[patched_1.16.5.jar:git-Paper-790]
at org.bukkit.plugin.java.JavaPluginLoader.disablePlugin(JavaPluginLoader.java:405) ~[patched_1.16.5.jar:git-Paper-790]
at org.bukkit.plugin.SimplePluginManager.disablePlugin(SimplePluginManager.java:533) ~[patched_1.16.5.jar:git-Paper-790]
at org.bukkit.plugin.java.JavaPluginLoader.enablePlugin(JavaPluginLoader.java:374) ~[patched_1.16.5.jar:git-Paper-790]
at org.bukkit.plugin.SimplePluginManager.enablePlugin(SimplePluginManager.java:500) ~[patched_1.16.5.jar:git-Paper-790]
at org.bukkit.craftbukkit.v1_16_R3.CraftServer.enablePlugin(CraftServer.java:518) ~[patched_1.16.5.jar:git-Paper-790]
at org.bukkit.craftbukkit.v1_16_R3.CraftServer.enablePlugins(CraftServer.java:432) ~[patched_1.16.5.jar:git-Paper-790]
at net.minecraft.server.v1_16_R3.MinecraftServer.loadWorld(MinecraftServer.java:599) ~[patched_1.16.5.jar:git-Paper-790]
at net.minecraft.server.v1_16_R3.DedicatedServer.init(DedicatedServer.java:298) ~[patched_1.16.5.jar:git-Paper-790]
at net.minecraft.server.v1_16_R3.MinecraftServer.w(MinecraftServer.java:1074) ~[patched_1.16.5.jar:git-Paper-790]
at net.minecraft.server.v1_16_R3.MinecraftServer.lambda$a$0(MinecraftServer.java:291) ~[patched_1.16.5.jar:git-Paper-790]
at java.lang.Thread.run(Thread.java:833) [?:?]