I dont know why I cant stop timer by handle on client

I set them on server, and run on server too,but it still doesnt work.Can someone tell how to sovle it?

If the server is owning the timer / function (Which is the most likely scenario here), the client won’t be able to stop the timer. You would have to send a request from the client to the server, and then ask the server to stop it. If all other players are affected, you would have to notify all other clients as well. Multicast would work in that case.