Ensure that your MacBook is signed on with the same Apple ID as your iPhone
Activate Messages on your MacBook. You can do this by opening the Messages app on your MacBook and then going into Preferences.
On your iPhone, open Settings ➔ Messages ➔ Text Message Forwarding: Ensure that your MacBook is listed and it is set to ON.
Do you use iCloud for Messages on your iPhone? If YES then open Settings ➔ Apple ID (Your Name at Top) ➔ iCloud ➔ Messages: Ensure that this is set to ON.
Ensure that your MacBook is signed on with the same Apple ID as your iPhone
Activate Messages on your MacBook. You can do this by opening the Messages app on your MacBook and then going into Preferences.
On your iPhone, open Settings ➔ Messages ➔ Text Message Forwarding: Ensure that your MacBook is listed and it is set to ON.
Do you use iCloud for Messages on your iPhone? If YES then open Settings ➔ Apple ID (Your Name at Top) ➔ iCloud ➔ Messages: Ensure that this is set to ON.