avd manager error

Dear Master I have following standar on installation the instruction including download Haxm and install it but i still have problem with my Emulator when im start from AVD Manager im find problem like above of this picture and i really need the advice cause im newbie.

im trying to my avd manager and im getting this error. sdk manager version is 3.20,java is updated, android platform is 24 right now, but i already changed platforms to 21 to 27. nothing is changed. thanks