Hi there!
Does the G-DRIVE show in System Information?
To find out, choose About This Mac, available from the Apple menu in the upper-left corner of your screen. Then choose More Info, and scroll down to select System Report. Look for "USB" in the sidebar of System Information, and see if the G-DRIVE appears in the USB Device Tree.
If it does, does it appear in Disk Utility?
To find out, in the Finder, choose Go > Utilities, then double-click the Disk Utility icon. (Disk Utility is located in the /Applications/Utilities folder.) Alternatively, click Launchpad in the Dock, type Disk Utility in the search field, then click the Disk Utility icon. Once Disk Utility is open, look for the G-DRIVE in the external drive section of Disk Utility.
-Jack