Spin-orbit coupling is not included in 12.8, only the basic noncollinear model. Also please note that there are some unresolved known bugs in the NC model in 12.8. Some will be fixed in 12.8.1, but not all - we ask users to be a little bit patient and wait for ATK 13.8 to use NC properly. Preview versions of that will be available by the early summer, and in the final 13.8 release there will be spin-orbit too.