Paid Ranks Default Ladder not enabled

Ok the plugin is paid ranks and Whenever a user from a rank does /rankup to get to B it says invalid args default ladder not enabled in the rankprices.yml but it is ill post the consign below please help I'm so lost.
Ladders:
Prison:
RequiredRank: A
Default: true
Ranks:
A:
Price: 0
B:
Price: 1000
C:
Price: 5000
D:
Price: 10000
E:
Price: 20000
F:
Price: 50000

 

Please use www.hastebin.com or otherwise we can't see your spacing.

What version of PaidRanks are you using?

 

The latest Version
and heres the haste bin link http://www.hastebin.com/cusebenuho.vbs

 

jake2829 No. I don't actually know what the "latest" is, there appear to be at least three different forks on dev.bukkit.org