Problem/Bug Nobody is able to attack anyone

A few hours after I downloaded the OldCombatMechanics plugin, the pvp on the server just stopped.
Shooting players with flame bows still set them on fire, though.
Just no knockback, or damage (as if they were in creative)

Plugins:
Announcers
bHome
mcMMO
BetterMaxHealth
deathcraft
EasySetSpawn
EnderContainers
Zenchantments
ExtraHardMode
HeadDrops
Titlebar
HolographicDisplays
Tablist
JoinMessagePlus
TPA
LockettePro
StackableItems
LuckPerms
SimplePrefix
MobEggDrops
SilkSpawners
NickNameX
SafeTrade
OpenInv
OresPlus

Along with this, the name color from the team color on /scoreboard has been removed, although the color tag is still present and players are still on the specific team..