on last build (spigot & essentialsx ) on startuo i have :

[11:07:16 ERROR]: Could not load 'plugins/EssentialsXGroupManager-2.0.1.jar' in folder 'plugins' org.bukkit.plugin.InvalidDescriptionException: Invalid plugin.yml at org.bukkit.plugin.java.JavaPluginLoader.getPluginDescription(JavaPluginLoader.java:154) ~[spigot-1.9.jar:git-Spigot-87e2f47-ef13ca4] at org.bukkit.plugin.SimplePluginManager.loadPlugins(SimplePluginManager.java:133) [spigot-1.9.jar:git-Spigot-87e2f47-ef13ca4] at org.bukkit.craftbukkit.v1_9_R1.CraftServer.loadPlugins(CraftServer.java:296) [spigot-1.9.jar:git-Spigot-87e2f47-ef13ca4] at net.minecraft.server.v1_9_R1.DedicatedServer.init(DedicatedServer.java:201) [spigot-1.9.jar:git-Spigot-87e2f47-ef13ca4] at net.minecraft.server.v1_9_R1.MinecraftServer.run(MinecraftServer.java:527) [spigot-1.9.jar:git-Spigot-87e2f47-ef13ca4] at java.lang.Thread.run(Thread.java:745) [?:1.7.0_80] Caused by: java.io.FileNotFoundException: Jar does not contain plugin.yml ... 6 more
i'm on java 7

I get the same thing.

Getting same...

I believe i have same problem too. the /pl does not show GroupManager in the list, new folder of groupmanager does not get created in the FTP(after backup downloaded) and no one can do any commands. i have tried /manuadd or whatever group managers commands it will tell you there is no such command or so.
pastebin:
http://pastebin.com/ap1QkWVF
Screenshot of no folder:
https://snapr.pw/i/322e4bd3ca.png

@drtshock

➜  ~  unzip -l ~/Downloads/EssentialsXGroupManager-2.0.1.jar | grep plugin.yml | wc
      0       0       0

rip. must not have included the plugin.yml. will fix.

Fixed a5686a1

Same here.... Identical..