[01:08:09] [Server thread/ERROR]: Fatal error trying to convert AetherGen v1.1:me/Logaaan/AetherGen/CustomGen.class
org.bukkit.plugin.AuthorNagException: No legacy enum constant for GRASS_BLOCK. Did you forget to define a modern (1.13+) api-version in your plugin.yml?
	at org.bukkit.craftbukkit.v1_15_R1.util.Commodore$1$1.visitFieldInsn(Commodore.java:294) ~[patched_1.15.2.jar:git-Paper-146]
	at org.bukkit.craftbukkit.libs.org.objectweb.asm.ClassReader.readCode(ClassReader.java:2419) ~[patched_1.15.2.jar:git-Paper-146]
	at org.bukkit.craftbukkit.libs.org.objectweb.asm.ClassReader.readMethod(ClassReader.java:1492) ~[patched_1.15.2.jar:git-Paper-146]
	at org.bukkit.craftbukkit.libs.org.objectweb.asm.ClassReader.accept(ClassReader.java:717) ~[patched_1.15.2.jar:git-Paper-146]
	at org.bukkit.craftbukkit.libs.org.objectweb.asm.ClassReader.accept(ClassReader.java:401) ~[patched_1.15.2.jar:git-Paper-146]
	at org.bukkit.craftbukkit.v1_15_R1.util.Commodore.convert(Commodore.java:173) ~[patched_1.15.2.jar:git-Paper-146]
	at org.bukkit.craftbukkit.v1_15_R1.util.CraftMagicNumbers.processClass(CraftMagicNumbers.java:293) ~[patched_1.15.2.jar:git-Paper-146]
	at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:144) ~[patched_1.15.2.jar:git-Paper-146]
	at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:100) ~[patched_1.15.2.jar:git-Paper-146]
	at java.lang.ClassLoader.loadClass(ClassLoader.java:424) ~[?:1.8.0_171]
	at java.lang.ClassLoader.loadClass(ClassLoader.java:357) ~[?:1.8.0_171]
	at java.lang.Class.forName0(Native Method) ~[?:1.8.0_171]
	at java.lang.Class.forName(Class.java:348) ~[?:1.8.0_171]
	at org.bukkit.plugin.java.PluginClassLoader.<init>(PluginClassLoader.java:68) ~[patched_1.15.2.jar:git-Paper-146]
	at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:134) ~[patched_1.15.2.jar:git-Paper-146]
	at org.bukkit.plugin.SimplePluginManager.loadPlugin(SimplePluginManager.java:397) ~[patched_1.15.2.jar:git-Paper-146]
	at org.bukkit.plugin.SimplePluginManager.loadPlugins(SimplePluginManager.java:305) ~[patched_1.15.2.jar:git-Paper-146]
	at org.bukkit.craftbukkit.v1_15_R1.CraftServer.loadPlugins(CraftServer.java:358) ~[patched_1.15.2.jar:git-Paper-146]
	at net.minecraft.server.v1_15_R1.DedicatedServer.init(DedicatedServer.java:234) ~[patched_1.15.2.jar:git-Paper-146]
	at net.minecraft.server.v1_15_R1.MinecraftServer.run(MinecraftServer.java:885) ~[patched_1.15.2.jar:git-Paper-146]
	at java.lang.Thread.run(Thread.java:748) [?:1.8.0_171]