How to add event to npc animation?

I tried to add event to npc animation but it did nothing only one time the event caller worked but animation didnt. this is my code and it is clasic script and is parent of npc root file

print("ok")
    local ready=false;
    while true do

        if game.Lighting.ClockTime < 8 then 
            --print(game.Lighting.ClockTime,game.Lighting.ClockTime <8)
            ready=true; 
        end
        if game.Lighting.ClockTime >=8 and ready==true then 
            ready = false;
            local an = workspace.Script.Mistr88.AnimSaves.ExportAnim --Instance.new("Animation");
            --an.AnimationId="6867865bca81889ad6c3d53cfe174b07";
            local a = workspace.Script.Mistr88.Humanoid:LoadAnimation(an)
            print("now")
            a.KeyframeReached:Connect(function(value)
            print(value)
            end)
            a:Play();

        end
        wait(1);
    end