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