I have no idea what I'm doing wrong, I've set up the groups, I've set up the group's prefixes, but they arent displaying the prefixes in game - What it says is [world] (ign) >> ______
The plugins we have installed are:
BF - Folder
CoreProtect - Folder
Essentials - Folder
HolographicDisplays - Folder
LuckPerms - Folder
Multiverse-Core - Folder
OpenInv - Folder
PlayerHeads - Folder
PluginMetrics - Folder
Updater - Folder
WorldEdit - Folder
WorldGuard - Folder
bStats - Folder
ArtMap-master.zip
CoreProtect-2.16.3.jar
EssentialsX-2.16.1.0.jar
HolographicDisplays.jar
LuckPerms-Bukkit-4.4.1 (1).jar
Multiverse-Core-3.0.0-SNAPSHOT.jar
OpenInv.jar
PlayerHeads.jar
votifier-1.9.jar
worldedit-bukkit-7.0.0-beta-05.jar
What should I do?

You need to have Vault installed.
LuckPerms provides the prefixes through Vault so that other plugins can use it.

Alright thank you

I downloaded the vault.jar but it still seems to not be working

You need to install a chat formatting plugin too. ;)

https://github.com/lucko/LuckPerms/wiki/Prefixes,-Suffixes-&-Meta#displaying-prefixes-and-suffixes