Hello Partenoboy71,
There are a few steps we can offer here in the Apple Support Communities that may help to resolve the issue. Though it looks like you've already done a lot of great steps on your own.
Start by opening the App Store, and look to see if you have any app updates available. If so, please complete the app updates. How to manually update apps on your Apple device - Apple Support. Test to see if the issue remains.
If the issue remains, you'll want to contact WhatsApp Support at this point. Since the WhatsApp app isn't developed by Apple, we'd recommend that you contact the app developer directly to investigate this further with you. They'd be best suited to help. Reference this link to learn How to contact an app developer. How to contact an app developer - Apple Support.
Kind regards!