Ring Video Doorbell (2nd Generation) isn't working but online and strong wifi signal

About one week ago, my hard-wired Ring Doorbell isn't working few hours every day.Recently isn't working at all.However, from my router, I can see the Doorbell has very good connection. It is assigned an IP address, and I can ping it. Also, all my other Ring Stick-up Cameras, which connect to the same Wi-Fi, are online and works fine.I can see obviously all motion are detected and all live views listed out but no video was recorded / viewed, no motion notification received and got no RING notification.I did all what I expected.- Reset.- Reconnect.-Remove / add device.but nothing is being changed. still online but not working.