I don't quite understand everything you're describing, but here's a couple of simple checks regarding the mobile only (text) portion of your setup:
1) make sure you have good mobile coverage (sounds like the car is OK)
2) make sure your provider isn't BLOCKING the message from the Nissan server (these are called "common short codes"--notice it's a 5 digit number and not a phone number--and need to be setup on BOTH ends) and the server knows it can send the message
If you're getting the emails, you should get the texts (assuming everything above is correct)