that's the part that's driving me up the wall too. We're seeing the same thing across about 130k random CRM leads - no consistent pattern whatsoever.
We've run a mini A/B test internally with personal test numbers that are actively using WhatsApp. some marketing templates fail on them, while the very same numbers receive different templates just minutes later without issue. So the number is clearly reachable and not on any opt-out or block list.
My working hypothesis is that Meta is doing dynamic engagement-based filtering per individual message template, rather than a straightforward contact-level opt-out or account quality check. would love to hear if anyone's managed to isolate the signal
