How can I trouble shoot "Your message could not be sent. #### is not registered with iMessage"?
Solution 1:
On your phone, go to Settings -> Messages -> Text Message Forwarding and make sure that "Text Messaging Forwarding" is turned on for your system.
Solution 2:
2 possibilities…
- Check you are sending to their phone number, not Home, or email address etc & that that specific 'detail' has a 'speech bubble icon'
Check in your address book that you are by default sending to the address that has a 'speech bubble' in Contacts > [specific name]
sorry for all the blur…
it may be the default is the one with the grey star, but I'm not certain how you would change that
- On your Mac, Messages, make sure their contact 'banner' isn't in red - if so, you need to select, or even possibly re-select, the correct contact number/email etc
Additionally, make sure their phone number is listed as 'iPhone' in their Contact Card.
More blur…
Solution 3:
For me, I needed to go into my iPhone's Settings > Messages and toggle iMessage OFF and then back on again. My mac then prompted me asking if I wanted to add my own iPhone's number for iMessage use ... I selected yes and bing.
Solution 4:
On your phone: Under Settings > Messages, make sure you have "Send as SMS" turned on.