whatsapp not working on cellular data

I am still using iPhone X. after os was upgraded to 14.2. Both WhatsApp and Telegram stopped connecting on cellular mode, but they worked well with Wi-Fi. I surf the net and did all the methods I found, including reinstallation of app, But WhatsApp still not working. Why?

And a weird thing was found. on setting- cellular page, I turned WhatsApp on, it changes to the green. But it turns off by Itself when I change other apps state.

Why?

Anyone can help me?