Check your phone’s internet connection.
Sometimes, WhatsApp can get locked or frozen.
This makes it appear as though the app can’t connect.
Delete the app cache.
A corrupted or full cache can cause all sorts of problems.
A bug fix might be waiting to be applied that can fix the problem with WhatsApp.
If updating doesn’t address the connection issue, you could have a problem with your current installation.
To delete the app, simply press and hold its icon to find the option to remove it.
Then, download it again from the app store: