Script is not increasing a value and doing as it should, with no errors?

I tried making a ranking system, and the script is supposed to increase a value in the player called "xp"

These are the ranks (they might have to do with the error):

local ranks = {
    Student = {
        XPneeded = 0;
        Rank = 1;
    };
    Janitor = {
        XPneeded = 100;
        Rank = 2
    };
    CafeteriaHelper = {
        XPneeded = 150;
        Rank = 3;
    };
    Teacher = {
        XPneeded = 220;
        Rank = 4;
    };
    Nurse = {
        XPneeded = 280;
        Rank = 5;
    };
    Secretary = {
        XPneeded = 350;
        Rank = 6;
    };
    Principal = {
        XPneeded = 500;
        Rank = 7;
    };
}

And this is the rank function (in module script):

function module.giveXPOrRankPlayer(plr,amount)
    -- Pop up
    local gui = game.ReplicatedStorage.UI.GainNotif:Clone()
    gui.Parent = plr.PlayerGui
    gui.TextLabel.Text = "+"..amount.." XP"
    gui.FireTweenAndTrans:FireClient(plr)
    -- Rank and XP stuff
    plr.Value = plr.Value + amount
    print(plr.Name.." has been given "..amount.." XP")
    for i, rank in pairs(ranks) do
        if plr.XP.Value >= rank.XPneeded then
            if ranks[i] == plr.Rank.Value then
                local nextRank = i+1
                plr.Rank = ranks[nextRank]

                local converted = tostring(rank)
                print(plr.Name.." has ranked up to "..converted..", "..plr.XP.Value.." XP")
            end
        end
    end
end

Why doesn't the script increase the value/xp?