What you see
When you turn on your Surface, it boots to UEFI (Unified Extensible Firmware Interface) and displays:
Couldn't find a bootable operating system. Check the Boot configuration to try to fix this.
Solution 1: Check the configuration
Select OK to dismiss the dialog and then select Boot configuration from the menu on the left. Ensure that you have a valid boot device selected. By default, all the options including Windows Boot Manager, Internal Storage, USB Storage, and PXE Network should be selected.
If Windows doesn’t start: Go to Solution 2.
Solution 2: Force restart
Press and hold down the power button until your Surface restarts and you see the Windows logo screen (this takes about 20 seconds), then release the power button. For more info, see Force a shutdown and restart your Surface.
If Windows doesn't start: Go to Solution 3.
Solution 3: Reset your Surface using a USB recovery drive
Start your Surface by using a USB recovery drive. Insert the USB recovery drive into the USB port on your Surface, then press and hold the volume-down button while you press and release the power button. When the Surface logo appears, release the volume-down button. For more info, see Creating and using a USB recovery drive for Surface.
If Windows doesn't start: Go to Solution 4.
Solution 4: Request Service
If these steps don't resolve the problem, you can submit a service request to Microsoft.