WhatsApp works after uninstalling and reinstalling – what to do?

iPhone 7. iOS 15.8.3 – The app could no longer be launched; only a notification popped up asking for an update. The update didn't work, though. I uninstalled and reinstalled it. Now, when I start the app, the following message appears and I can't go any further. Both links lead to the WhatsApp website – you just go around in circles, but you can't link your device and continue because there's no button. I'm confused and I'm fairly experienced.

Thanks for your help.