Simple Prefix not working

groups:
Guest:
default: true
permissions:
- modifyworld.*
- essentials.kit
- essentials.balance
- essentials.afk
- essentials.help
- essentials.helpop
- essentials.info
- essentials.list
- essentials.motd
- essentials.rules
- essentials.spawn
- essentials.me
- essentials.warp
- simpleprefix.Guest: true
Member:
inheritance:
- Guest
permissions:
- essentials.msg
- essentials.tpa
- essentials.tpaccept
- essentials.tpdeny
- essentials.sethome
- essentials.home
- simpleprefix.Member: true
Mod:
inheritance:
- Member
permissions:
- essentials.tempban
- essentials.mute
- essentials.togglejail
- essentials.kick
- simpleprefix.Mod: true
users:
Dawg00chief:
group:
- Guest

orlds:
world:
nickname: '&e[World]&f'
Group:
Guest:
prefix: '&7[Guest]'
suffix: ''
Member:
prefix: '&6[Member]'
suffix: ''
Mod:
prefix: '&1[Mod]'
suffix: ''