I'm having the same problem. I picked up my car end of June (LTE) enabled. I tried the "hold both scroll wheels to reset approach x3, while driving, parked, held until "T" appeared on screen, long enough for both dash and console reset" and no luck.
I found the post below on how to fix, but I wanted to have the service center confirm the steps and the process. I scheduled an appointment (they told me to plan on 2 hour window to fix), and then my LTE started to work. I cancelled, and 2 days later it was out again. So I drove the car to the service center. I talked with mechanic, he was very helpful and polite. It only took 15 minutes from start to finish and looks simple. He followed the procedure below, so i know it is safe.. If this is going to be a re-occuring issue, I think Tesla needs to provide a good old fashion $.25 on/off switch to perform the reset.
I was told by SC this is clearly this is an issue with software updates. The mother ship fixes some bugs and breaking other items. Argh!
Good luck.
Originally Posted by
yoyo 
Here is what I got from SC that fixed the issue. SC suspect that it is the latest firmware related and have been at least 2. I did not want to drive to SC so they walked me through over the phone. It required pulling the fuse for the MCU.
1) open the fuse box in the frunk on the
passenger side. You see a bunch of colorful fuses in the red box.
2) The
yellow 20amp fuse for MCU is in the
top row (closest to the windshielf), 4th column counting from the right side (you are facing it, so the right side is toward the middle of the car). It is yellow color. Below it is a green 30amp. On its right is a green 30amp, and on its left is a brown 5amp. Make sure you identify the right one.
3) use a pliers to pull it out
4) leave it for at least
3 minutes --- make sure over 3 minutes
5) push it back, and the MCU will reset itself