Sometimes gnome-disk-utility will does not update partition info after re-partitioning a disk. For example, attach a blank usb drive to a vm and then run an installation. The installation will re-partition the disk but gnome-disk still shows the drive as blank (which should probably be reported as a bug).
blockdev --rereadpt /dev/sdX
These following commands do update the kernel, but do not solve the issue with gnome-disk-utility. Seems like the kernel is not notifying the d-bus layer or something…
# partprobe /dev/sdX#
hdparm -z /dev/sdX#
sfdisk -R /dev/sdX