cannot stop CPU on STM32F205ZE using ST-Link-V2

I am trying to work on simple HelloWorld project for STM32F205ZE. I have set ST-Link-V2 driver properly as I can permanent red light on St-Link-V2 . I am able to build project propely but when I try to execute, I get "cannot stop CPU" and no breakpoint gets set up in the code.

As long as I am understand I have done all things correctly. Other articles on "cannot stop CPU" are not properly answered. Please help me in this issue.