We have implemented a workaround on our side which would allow connecting WhatsApp channel to ManyChat.
We will be monitoring the situation for some time before closing this incident.
Investigating · UTC
WhatsApp channel can't be connected to ManyChat at the moment - we're experiencing the issue with WhatsApp’s Embedded Sign-Up mechanism, which doesn't return a web-hook with Business data at the very last step of the process.
Our team is working to resolve this issue with Meta - more information to follow soon.