I have followed the instruction of the user guide here (https://developer.apple.com/library/content/documentation/DeveloperTools/Conceptual/InstrumentsUserGuide/MeasuringEnergyImpact.html), tring to get some energy usage data with power unplugged, but every time I import the data from device, the "energy usage level" row is empty while other row like CPU Activity data is collected normally. Any idea how to fix this?
OSX version 10.11.6 (15G1212)
Xcode & Instruments version is 8.2.1 (8C1002)
Device is Iphone7 10.2