Sometimes because of:
Password changes
WhatsApp gettings logged out of everywhere
Bugs with WhatsApp API
Meta revokes the permission from Spur to access your account, in that case you can simply give us the permissions again
Go to Settings > WhatsApp
Select your channel
Scroll down and hit "give WhatsApp permissions again"
This will open a Facebook popup and you'll have to give us permissions again, and that should fix the issue & your messaging will be back live