Workspace.AdmindCommands.Ban:42: bad argument #1 to 'insert' (table expected, got nil)?

I don't know what the problem is, this is the error: Workspace.AdmindCommands.Ban:42: bad argument #1 to 'insert' (table expected, got nil)

This is the code (serverscript), this is linked to a local. I made a lot off comments, mostly to help myself to navigate trough this too long script, I added a comment too on places that give an error

I want to insert the name of the player in that table and then save it.

local ReplicatedStorage = game:GetService("ReplicatedStorage")
local banEvent = ReplicatedStorage:WaitForChild("AddBan")

local DataStore = game:GetService("DataStoreService")
local BanlistSave = DataStore:GetDataStore("BanlistDataStore")

banList = {}
globalKey = 1092 -- If you want to clear this datastore just change this value

unbanList = {} -- Add names to this list if you want them to be unbanned, load the server, then remove them

function getBanList()                               
    banList = BanlistSave:GetAsync(globalKey)                    -- Sets the table to the save file
end

if unbanList ~= nil then                  -- Checks if unbanlist is empty
    getBanList()
    for index, unban in pairs(unbanList) do
        for index, ban in pairs(banList) do
            if unban == ban then          -- Checks if player is actually banned
                table.remove(banList,ban) -- If so, remove the player out of the table
            end
        end
    end
end

game.Players.PlayerAdded:connect(function(plr) -- Player joined
    getBanList()                               -- Refreshed the banlist
    wait(1)
    for index, bannedPlr in pairs(banList) do  -- Checks if the name of the player is the same as a name out of the banlist
        print(bannedPlr)
        if plr.Name == bannedPlr then
            plr:Kick("Your banned. If you think this is an error please contact one of our admins!") -- Kick if neccesary
        end
    end
end)

banEvent.OnServerEvent:connect(function(player, TargettedPlayer) -- Bans player on remote event
    warn('conection remote event ban')
    print("banning "..TargettedPlayer)

    table.insert(banList, TargettedPlayer)                       -- Adds name to datastore table PROBLEM IS HERE!!!!! 
    for index, gamePlayer in pairs(game.Players:GetPlayers()) do
        if gamePlayer.Name == TargettedPlayer then
            gamePlayer:Kick("admin "..player.Name.." has banned you. Believe this is an error? Message one of our admins!")  -- Kicks player
        end
    end

    BanlistSave:SetAsync(globalKey, banList)                     -- Saves the table
end)


while wait(1) do                                                 -- Updates list every second
    getBanList()
end