There can be numerous things.
It may have been partitioned but not formatted?
Has it been formatted on a linux system?
Has it been tried on another system?
Have you been using this before?
Go to Conputer Management and click on Disk Management.
If it tells you that the disk is Simple, Basic, NTFS it was formatted on a Windows machine.
Does it say Primary Partition? If not, then it hasn’t been formatted and formatting will need to be done to make the disc usable.