3tb set as gpt only showing only 2tb

Hello,
i got a wd green 3tb, when i first set it to gpt it show 2.7tb, but the file copied in to was given the wrong memory address, so it some times display the wrong documents, or wrong video, and even saying error and files does not exist.
so i reformatted the hard drive but it auto set to ntsf and was showing only 746gb, then i had to delete the partition and set it back to gpt and this time it only shows 2tb, and i had kept redoing it but it only keep showing the 2tb, so i am completely stuck
also disk management only show 2tb, the remaining 700gb is not showing up
any idea what is going on here?