CONTEXT
An iPhone and iPad are both:
- outfitted with a T-Mobile SIM card + Data
- configured with the same AppleID and
- presumably this ID is one's iMessage ID.
- IOS 12.X
As I understand it:
- Blue Messages are encrypted iMessages
- Green messages are unencrypted MMS / SMS
OBSERVATIONS
iPad message app indicates:
- iMessages are successful sent / received from and iPad's message app.
- iMessages are synced to iPhone
- green SMS / MMS fail to send: indication = "Not Delivered"
iPhone:
- iMessages /SMS / MMS function as expected
Goal = send SMS / MMS from the iPad.
Any diagnostic question, posted as a comment, is appreciated. Actionable guidance is sought.
Best Answer
Do you have text message forwarding enabled on your iPhone and iPad? If you go into the Messages settings on your iPhone, you will see some settings that you will need to enable in order to send SMS/MMS. Your iMessages are working because that only requires an Apple ID but you need to allow your iPad to send SMS/MMS via your cellular account from your iPhone. Good luck!