Plugin Help Groupmanager help?

I made a new rank ladder in my group manager groups and when i restart, groupmanager stops working. The rank that is new is B. Here is the file:
# Group inheritance
#
# Any inherited groups prefixed with a g: are global groups
# and are inherited from the GlobalGroups.yml.
#
# Groups without the g: prefix are groups local to this world
# and are defined in the this groups.yml file.
#
# Local group inheritances define your promotion tree when using 'manpromote/mandemote'

groups:
Default:
default: true
permissions:
- essentials.kit
- essentials.kits.Starter
- essentials.balance
- essentials.balancetop
- essentials.pay
- essentials.help
- essentials.helpop
- essentials.ignore
- essentials.msg
- essentials.suicide
- essentials.spawn
- essentials.warp
- essentials.warp.list
- essentials.warps.AMine
- essentials.warps.dp
- essentials.warps.pvp
- essentials.warps.pvpmine
- essentials.warps.info
- essentials.warps.staff
- plotme.use.claim
- plotme.use.auto
- plotme.use.biome
- plotme.use.clear
- plotme.use.comment
- plotme.use.dispose
- plotme.use.add
- plotme.use.remove
- prisonrankup.rankup
- prisonrankup.ranks.


inheritance:
- g:groupmanager_default
- g:bukkit_default
- g:essentials_default
- g:towny_default
info:
prefix: '&e&l<&a&l&o!&4&lA&a&l&o!&e&l>'
build: false
suffix: ''
Owner:
default: false
permissions:
- +vanish.effects.toggle.all
- -vanish.effects.*
- '*'
inheritance:
- admin
info:
prefix: '&8&l[&4&l&k;&2&l&oStaff&4&l&k;&8&l]'
build: true
suffix: '&8&l[&4&l&k;&c&l&n&oOwner&4&l&k;&8&l]'
Builder:
default: false
permissions: []
inheritance:
- default
- g:essentials_builder
- g:towny_builder
info:
prefix: '&2'
build: true
suffix: ''
Moderator:
default: false
permissions: []
inheritance:
- builder
- g:groupmanager_moderator
- g:bukkit_moderator
- g:essentials_moderator
- g:towny_moderator
- g:vanish_moderator
info:
prefix: '&5'
build: true
suffix: ''
Admin:
default: false
permissions: []
inheritance:
- moderator
- g:groupmanager_admin
- g:bukkit_admin
- g:essentials_admin
- g:towny_admin
- g:vanish_admin
info:
prefix: '&c'
build: true
suffix: ''
B:
default:false
permissions:
- essentials.warps.b
- essentials.kit
- essentials.kits.Starter
- essentials.balance
- essentials.balancetop
- essentials.pay
- essentials.help
- essentials.helpop
- essentials.ignore
- essentials.msg
- essentials.suicide
- essentials.spawn
- essentials.warp
- essentials.warp.list
- essentials.warps.AMine
- essentials.warps.dp
- essentials.warps.pvp
- essentials.warps.pvpmine
- essentials.warps.info
- essentials.warps.staff
- plotme.use.claim
- plotme.use.auto
- plotme.use.biome
- plotme.use.clear
- plotme.use.comment
- plotme.use.dispose
- plotme.use.add
- plotme.use.remove
- prisonrankup.rankup
- prisonrankup.ranks
inheritance: []
info:
prefix: '&e&l<&c&L!&9&lB&c&l!&e&l>
build: false
suffix: ''

 

I'm assuming it's a prison server, Why is your first group not called A?