CoreStorage: what does LVG status 'offline' and PV status 'checking' mean and how can it be fixed?
I had the same problem after converting a disk. There was a message displayed by diskutil cs convert:

Couldn't unmount disk0s4; converted volume won't appear until it's unmounted


I solved the problem by unmounting the disk and repairing it :

diskutil unmount force disk0s4
diskutil repairVolume disk0s4