I am attempting to run the ring resonator tutorial.The tutorial seems to indicate that the group index should be 4.63 near 1.55 um, but for whatever reason, I keep running it and getting the same group index of 4.79. I have checked the parameters I input several times and am fairly confident I am pressing the right buttons as outlined in the tutorial, which is leading me to wonder if it is possible that in the new release there is an updated setting which I need to switch on or off. Alternatively, if other people have had this problem before and it is simply that I am missing a step, please let me know which step.
Update: using multi-coefficient model in materials explorer does not change result.
The value that you find is reasonably close to the reported value. I followed the steps and my value was similar to the yours (make sure that your waveguide sits in the middle of FDE solver, I found a typo in the methodology about y-position of FDE solver).
There are few things that you can do to improve your value:
plot the simulated mode profile in log scale. You will realize that FDE boundaries, specifically in the z-direction, are small thus truncate the electric fields. You can set z-span of FDE solver to 2um, for example.
Increase your mesh size
Use a higher number of modes for better accuracy.
Hope this answered your question.