On my iPhone?
I can't see when someone texts me. It's like this when your phone is turned off and someone writes on WhatsApp, you see it on the lock screen. It doesn't work for me. Only when I open the WhatsApp app do the messages update and new ones appear, but I want to know who has written something beforehand, so I don't have to go into the app first. What's wrong?
Depends on what you set in settings, messages, WhatsApp. At least the button “Allow notifications” should be set to “In”.
Maybe you disabled the push notifications at Whatsapp