I have a Nexus 5 that won't go into Doze/IDLE mode using ADB commands from Windows. It's adb connected using USB cable and it is working for all other ADB commands. The screen is off.
C:\>adb shell dumpsys deviceidle force-idle
Unable to go idle; stopped at ACTIVE
C:\>adb shell dumpsys deviceidle enable
C:\>adb shell dumpsys battery unplug
C:\>adb shell dumpsys deviceidle step
Stepped to: ACTIVE
C:\>adb shell dumpsys deviceidle step
Stepped to: ACTIVE
C:\>adb shell dumpsys deviceidle step
Stepped to: ACTIVE
C:\>adb shell dumpsys deviceidle enable
C:\>adb shell dumpsys deviceidle force-idle
Unable to go idle; stopped at ACTIVE