I have the same error! when I use /ar check it says
"autorank is disabled, check your server.log!"
I copied and pasted new config files to remove any errors and it still is not working!

Here is my server log
http://pastebin.com/AmJdq1Bt

Closed due to inactivity.

It seems PEX can't start and therefore a bunch of other plugins crash, including Autorank.