I just had the same issue.  I put my XPS13 to sleep, then my Bluetooth mouse didnt work when I resumed and after numerous restarts. Had to disable "Fast start up" in the power options, as per post: www.tenforums.com/.../4189-fast-startup-turn-off-windows-10-a.html Wasted 2hrs of my life troubleshooting this.....sheeeshhh
Just cannot get Bluetooth to work with any device even though those devices work with each other.   It will see the device in the Bluetooth settings page and will get 'paired', then 'Connected' for about 5 seconds, then drop back to 'Paired'.  Never really gets a usable connection.    Everything else works well on this laptop.  I have downloaded a couple of drivers from the Dell site but not sure where to go from here.  Any help would be appreciated.
Bluetooth not working on new XPS 13 9350, Windows 10