We have identified an issue where WATI users sees an error "Resource not found. Could not retrieve phone number from contact store" when sending messages.
This error may happen for conversations that were originally initiated by the end-customer more than 7 days ago, ie end-customer sent the first message to the business number. WhatsApp has acknowledged to us the error comes from a specific version of the WhatsApp server being used and we are currently working with WhatsApp to identify the best version to use to avoid this error.