Blazor jsInterop addeventlistener for online works but not for offline

I have this js interop:

window.interop = {       registerOnline: function (instance) {        window.addEventListener('online', (e) => {            instance.invokeMethodAsync('CallSync');        });                  },    registerOffline: function (instance) {        window.addEventListener('offline', (e) => {            instance.invokeMethodAsync('Offline');        });    },    initialOnlineStatus: function () {        return navigator.onLine;    }};

and this is the c# part:

public async Task Register() {     var obj = DotNetObjectReference.Create(this);                await js.InvokeVoidAsync("interop.registerOnline", obj);     await js.InvokeVoidAsync("interop.registerOffline", obj);     IsOnline = await js.InvokeAsync<bool>("interop.initialOnlineStatus");            }

when I turn on wifi and wait, the online status works, but if I turn off computers wifi, the offline doesn't work.How to make offline event work?