Problem with boot disk

I loaded a .iso-file with Centos 7 to images.
Than created a template with the Centos7 iso-file and a Volatile disk in format raw.
After that i instantiated a VM from the template, setup Centos 7 from the iso-file to the raw disk.
Everything is ok, my VM loaded from the raw disk successful after installation.
And I want to save my installed VM as image, but when i create new VM she can’t load from the disk and says “Not a bootable disk”
Why is it happened?