I have started to get “Unable to boot device because it cannot be located on disk”
Use the device manager in Xcode or the simctl command line tool to either delete the device properly or erase contents and settings.
This happens on some of the simulator devices. Right now it won’t launch an ipad simulator.
Sorry - if you have the extra simulators installed then you should be able to create a new one with those
At least I could in Xcode 7 on 10.10 and 10.11