I had to finally do something about my Band 2 to not working well with my Lumia 950 today as they haven't played nice together in a while. Specifically I wasn't receiving text notifications on my Band and I couldn't use the action button to call up Cortana. Tonight I got the latest OS update (10.0.10586.107) and thought it would fix it. I was waiting to see if it would be fixed with this update before resetting my phone because that is basically what an OS update would do anyway. The OS update didn't help so here's how I solved each issue.
No Text Notifications on Microsoft Band 2:
On a Microsoft forum I read that someone had edited their privacy settings and after turning enough things back on for the Microsoft Health app, texts started working again. Based on this post I found that if I allowed Microsoft Health access to my Contacts, texts would start showing up!
Cortana Not working on Microsoft Band 2:
On a different forum I saw lots of information about resetting and re-pairing your band with your phone. I tried one of these and didn't have any luck. While on the Bluetooth pairing page I noticed the Advanced button at the bottom that displays a checkbox when clicked. The option is to "Use an alternate Bluetooth audio connection for Speech". I checked it, restarted the Band and Cortana worked on the Band! I couldn't believe it and thought that it shouldn't be necessary. I tried unchecking the box and Cortana still worked not to mention the keyboard problem when replying to texts from your Band. If you have seen the message on your Band "Make sure your bluetooth is on and your phone is close by" or one that I have only seen once "Enable voice in your bluetooth settings".
All in all I never had to reinstall Microsoft Health. I did reset my band and re-pair with a power down of both devices in between. So nice for it to all be working again...Like a Microsoft Band 1 with a Lumia 635 :-)