Where can I see Broadcast Statistics & SMS Fallback?
Click Broadcast Statistic button to view a broadcast results in details:

Use the filter to sort contacts by Status (Queued, Pending, Sending, Delivered, Failed):

To those contacts unreachable via WhatsApp, you may send a SMS message instead by clicking the checkbox of contacts and then click “Send SMS”.
Click "Export to CSV" to export Broadcast statistic to CSV file.