Please follow the steps below to activate WordPress WhatsApp Support:
In the file wordpress-whatsapp-support.php which is in the root of the plugin folder, after line 73 which is:
You can have whatever you like for the license key, it doesn’t do anything (the plugin merely checks for the existence of something, it doesn’t matter what it is!) so use whatever you want to show on the plugin registration field in the plugin support page.
It will be automatically activated when you reload the dashboard.