Q: cant switch OS

reboot and hold down the OPTION key.

If you are unable to boot into Windows please provide more details in your thread

Writing an effective Apple Support Communities question

Follow the advice above to force the selection on re-boot. You probably just have to re-install the Boot Camp utilities in Windows to regain the ability to select the switch there.

If you are no longer able to boot to OS X using the option key, Windows may have damaged the partition table on the drive. In that case, you may have to boot to recovery and wipe and reinstall OS X, then set up boot camp again and re-install Windows.

Windows has a habit of assuming it owns the entire machine and doing what it likes.

Yessov wrote:

 

i cant switch from windows 10 to OS X Yosemitie after recover windows

(no Boot Camp icon in tray)

(keyboard commands dont help)

If you recovered Windows and/or Reset W10, you will need to re-install Bootcamp6 drivers so you can get Apple services and hardware to function properly. You 'recover' seems to be to a System Restore point, before BC drivers were installed.

Please see If you don't see some Mac features when using Windows on your Mac - Apple Support for the necessary steps.

Please also see https://help.apple.com/bootcamp/controlpanel/5.1/ , for what functions should be available.