This occurs on 1.13 and 1.14 on Paper
[23:37:21] [Server thread/ERROR]: Could not load 'plugins\Multiverse-Portals.jar' in folder 'plugins'
org.bukkit.plugin.InvalidPluginException: java.lang.NoClassDefFoundError: com/onarandombox/commandhandler/Command
at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:138) ~[patched_1.14.4.jar:git-Paper-154]
at org.bukkit.plugin.SimplePluginManager.loadPlugin(SimplePluginManager.java:337) ~[patched_1.14.4.jar:git-Paper-154]
at org.bukkit.plugin.SimplePluginManager.loadPlugins(SimplePluginManager.java:257) ~[patched_1.14.4.jar:git-Paper-154]
at org.bukkit.craftbukkit.v1_14_R1.CraftServer.loadPlugins(CraftServer.java:355) ~[patched_1.14.4.jar:git-Paper-154]
at net.minecraft.server.v1_14_R1.DedicatedServer.init(DedicatedServer.java:218) ~[patched_1.14.4.jar:git-Paper-154]
at net.minecraft.server.v1_14_R1.MinecraftServer.run(MinecraftServer.java:869) ~[patched_1.14.4.jar:git-Paper-154]
at java.lang.Thread.run(Unknown Source) [?:1.8.0_131]
Caused by: java.lang.NoClassDefFoundError: com/onarandombox/commandhandler/Command
at java.lang.Class.forName0(Native Method) ~[?:1.8.0_131]
at java.lang.Class.forName(Unknown Source) ~[?:1.8.0_131]
at org.bukkit.plugin.java.PluginClassLoader.(PluginClassLoader.java:63) ~[patched_1.14.4.jar:git-Paper-154]
at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:134) ~[patched_1.14.4.jar:git-Paper-154]
... 6 more
Caused by: java.lang.ClassNotFoundException: com.onarandombox.commandhandler.Command
at java.net.URLClassLoader.findClass(Unknown Source) ~[?:1.8.0_131]
at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:139) ~[patched_1.14.4.jar:git-Paper-154]
at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:85) ~[patched_1.14.4.jar:git-Paper-154]
at java.lang.ClassLoader.loadClass(Unknown Source) ~[?:1.8.0_131]
at java.lang.ClassLoader.loadClass(Unknown Source) ~[?:1.8.0_131]
at java.lang.Class.forName0(Native Method) ~[?:1.8.0_131]
at java.lang.Class.forName(Unknown Source) ~[?:1.8.0_131]
at org.bukkit.plugin.java.PluginClassLoader.(PluginClassLoader.java:63) ~[patched_1.14.4.jar:git-Paper-154]
at org.bukkit.plugin.java.JavaPluginLoader.loadPlugin(JavaPluginLoader.java:134) ~[patched_1.14.4.jar:git-Paper-154]
... 6 more