I'm using the last version of EssentialsX in a server with plugins and mods (pixelmon), and I need to use /give pixelmon:poke_ball (example) but the console says that unknow item name: pixelmon:poke_ball. How I can solve this?
Thanks for reading!

We don't support hybrid server implementations (servers combining Bukkit with Forge).

To use plugins alongside Pixelmon, you should check out Sponge - you can see instructions on setting up a Sponge server over at the Sponge docs.