could not find developer disk image

Same issue here.... Any news????

Found the answer We need to upgrade Xcode..... LOL

Actually, this has been common as of late (over the last month or so), typically requiring a re-install, but stepping up to 7.2 would amount to the same thing, so glad you worked it out in any case.

This issue occurs when your version of Xcode has an unsupported device attached. This could happen for any number of reasons but the primary scenario is that you may have installed a newer version of iOS on your device while continuing to use an older version of Xcode. In either case you will note that each version of Xcode supports only certain devices. You can either copy or link the missing device support directory into the Xcode version that you are using. After performing this procedure you can then restart Xcode, plug in your device and open the Window > Devices display to verify that your attached device is recognized and fully supported. In most cases this will take a few minutes as Xcode builds the symbols needed to install software onto the device.

Creating a link to the valid device directory if you have both the beta and the production versions of Xcode installed

Open Terminal (Finder > Go > Utilities > Terminal) or In Spotlight type terminal

Login as a super user within terminal

sudo ln -s /Applications/Xcode-beta.app/Contents/Developer/Platforms/iPhoneOS.platform/DeviceSupport/10.0\ \(14A5261u\) /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/DeviceSupport

How to Copy the new device support folder for the missing version of iOS running on your device.

How to Open Source Folder

Open a new Finder Window (Finder > File > New Finder Window)

Open the following Xcode beta source folder in Finder (Finder > Go to Folder...> paste in the following path)

/Applications/Xcode-beta.app/Contents/Developer/Platforms/iPhoneOS.platform/DeviceSupport

This will show you all of the devices supported by the current beta version of Xcode. You will need to copy the new device folder from this location.

How to Open Target Folder

Open the following Xcode target folder in Finder (Finder > Go to Folder...> paste in the following path)

/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/DeviceSupport

This will show you all of the devices supported by the current version of Xcode. You will need to paste the new device folder into this location.

How to Copy the Device Support Between Source and Target Folders

Select the missing device folder from your Source Folder that you want to appear in the other version of Xcode

Copy the source device folder

Paste the device folder from the source directory tinto your target folder