Messaging Window (For Official WhatsApp Only)
Official WhatsApp has a messaging window of 24 hours which allow users to reply to customers with any content using session messages.
For Official WhatsApp, there will be a notification on the bottom of the reply screen indicating when you have a chat window of 24 hours with the customer to send any "Session Messages".
Session Message 24 Hour Notification
However, if the client does not reply to you after 24 hours, the notification on the bottom will change, and you will have to send "Template Messages" until they respond.
If you want to know more about Official WhatsApp, you can check the below guides.