Enhanced WhatsApp Channel Activated but Outbound Messages Fail — "Can't send messages from this channel"

Hi all, 

I've built an Agentforce Service Agent connected to WhatsApp via an Enhanced Messaging channel, and I'm stuck on a specific outbound failure after getting past several other setup hurdles. Hoping someone's hit this exact combination before.

Setup:

• Enhanced WhatsApp channel, Meta Business Account connected, number verified
• Routing Type: Omni Channel Flow -> Agentforce
• Fallback Queue configured with a Routing Configuration attached 

What's working:

• Inbound messages from WhatsApp are reaching Salesforce fine — I can see Messaging Sessions being created (MS-00000001, etc.) with correct timestamps and the customer's message logged
• Delivery checkmarks show on WhatsApp (message reached Meta)

What's broken:

 Every attempt to send anything back to the customer — including the standard opt-in prompt — fails with:

 "Can't send messages from this channel. Ask your admin to check the channel settings and contact Salesforce Customer Support."

 — logged as Automated Process

So it looks like an asymmetric failure: inbound works, outbound doesn't. I've already tried:

• Refresh Connection on the channel (no change)
• Re-registering the messaging session
• Confirming the channel shows as Active in Messaging Settings
• Double-checked Automated Response components are correctly linked (not free-typed text) 

Has anyone run into this specific "Can't send messages from this channel" error on an Enhanced WhatsApp channel where inbound works but outbound doesn't? Trying to figure out if this is a Meta-side WABA/token issue or a Salesforce-side channel misconfiguration before I open a formal support case.

Appreciate any pointers — happy to share more config details if useful. 

@* Service Cloud *