Weird Bug: No Message Button on Client's FB Page + ManyChat Automation Dead Silent

One useful fact in your screenshots: the "couldn't send" happened on a manual message from a personal account. ManyChat isn't involved in that path, so whatever this is sits at the Page level, and the automation not firing is a symptom, not the disease.

Given the page size, the most likely cause: if that automation was recently sending a high volume of DMs, especially near-identical ones, Meta rate-limits and can restrict messaging on the Page itself. When that happens the Message button disappears and sends fail exactly like your screenshot. I've seen this firsthand on a page that blasted the same DM too many times. Check the Page's Support Inbox and account status in Business Suite for a messaging restriction notice. These usually lift on their own after days to a few weeks, and pushing more volume before it lifts extends it.

If there's no restriction notice, run down the config causes: the "allow people to contact my Page" toggle (it's what shows the Message button), and any country or age restrictions on the Page, both hide the button and block sends. And as a sanity check, have someone else message the Page from a different account to rule out the testing account itself.

Once a manual message goes through, the automation should fire again without touching anything in ManyChat. When it does, vary the DM text and pace the sends, that's what keeps this from recurring.

Yes it was “Allow people to conatct my page” things.

Thanks