If you are using a iXpand USB 2.0 drive you may need a FW update. If you do not have an iOS 8 device to update with you will need a PC to update. Please see the FW update tool for PC linked below.
i also have the same issue, my iXpand shows Firmware Version 4.4.8, and the Model Number shows SanDisk iXpand Flash Drive 16GB, and my iPad Version is 9.3.2.
But my iPad does not recognise the iXpand drive.
When the drive is inserted the SanDisk App starts, with the message, “Hello! Plug in your iXpand Flash Drive to get started!”