Close the app in the background, go to Settings > open WhatsApp settings > go to storage > clear cache. Then permissions > disable all permissions > force stop application.
Now, go to WhatsApp. You should see that every contact has no name. Go to contact list (in WhatsApp), it will say to accept the permission for accessing contacts. Now it ...
I recently had a similar issue on my Samsung Galaxy S21 with Android 12.
For months the built in Contacts app would sync correctly with Office 365 via the Outlook app, but suddenly it stopped working, my contacts all disappeared, and wouldn't update.
Contacts showed that the last sync had just happened.
Things that did NOT help:
On every Android device I have worked with there was always an option to force synchronization of Google data in the settings of the account:
Open Android settings and navigate to the account list. Open the used Google account and then it's "Account sync" page (synchronization settings).
There you can enable/disable each synchronization category ...
Google's Fix sync errors with the Gmail Android app's last resort ("Only follow these steps if the above steps didn't work") solved it for me!
However, it initially led to confusion since it seems to refer to obsolete settings.
The correct "last resort" steps are:
Open your device's Settings app.
Tap Apps & notifications > See All ...