Had the same problem yesterday. Took almost 12 hours to get it working.
Tried dozens of things - then it got activated, stopped again, activated, stopped .. and so on.
Suddenly *poof* working.
Same issue for me. I downgraded to 9.01 and still having this issue. FML.
Towards getting this bug fixed, it would be good to report it via either the Feedback Assistant app or with https://bugreport.apple.com.
In the meantime, a workaround that has fixed many such issues for people on 9.1b1 & 2 is to make a new iTunes backup and then reset to "factory condition" (as Apple put it) with Settings > General > Reset > Erase all Content and Settings, and after that restoring from the iTunes backup.
Let me know how it goes,