WD My passport 1TB only has 500GB

My brand new WD My passport 1TB is not letting me copy an 8GB file to it or other large files either although only 500GB have been used after copy this yesterday and so 431GB should be available on this brand new drive.
I ran chkdsk and got below which indicates there shouldnt be a problem but I cannot use the 431 GB :

Windows has scanned the file system and found no problems.
No further action is required.
976,608,256 KB total disk space.
822,656 KB in 7,646 hidden files.
3,938,112 KB in 61,452 folders.
582,898,240 KB in 543,480 files.
388,949,184 KB are available.

   65,536 bytes in each allocation unit.

15,259,504 total allocation units on disk.
6,077,331 allocation units available on disk.

Hi @rdsk
Have you opened a Support Case? If not opened, for more information, please contact the WD Technical Support team for the best assistance and troubleshooting:

Hi, the drive is fine. the issue was sth to do with the encryption. Reformatted and reencrypted and now 100% fine. Thanks for your help