Plugins feature not working

[CobraSteal]

I went on eu.mcpvp to see what practice plugin they used as I am making my own server. Anyway I kept on getting this message in chat every time I tried to use the client's plugins feature:

[kawaiinekololis]

@CobraSteal This means the server has patched the exploit.

The message looks like that because the translation seems to be missing... whoops