Hi,
If you checked that bootable volume has selected when creating volume, then you can try press 'Next' button if it's not grey.
But IOE, if you're going to make this image as public after build, note that it may become a problem because you can't modify visibility for image uploaded from volume.
Also, we don't know if Ceph storage method changed in Victoria or not. But in Rocky, upload volume to image will just create a RBD snapshot from volume in Ceph layer.
That means you can't delete that volume unless delete the child image first in the future.
Because the above reason, we still suggest using Linux KVM to build Windows image.