Some sad news here. We don’t support Auto Send for Whatsapp or Facebook Messenger. Even though we'd love to facilitate it, Whatsapp and Facebook don’t allow us to ☹️.
Schedule a message via Whatsapp or Facebook Messenger without Auto Send
You cán however schedule messages for Facebook Messenger and WhatsApp by scheduling messages without using the Auto Send feature:
Write and schedule a message
At the moment you scheduled the message, you get a notification
Tap the notification and confirm that you want to send the message
Choose which messenger you'd like to use to send it with, like Whatsapp or Facebook.