Can't find internal HDD in my computer, letter disappears on reboot

cannot find internal hard drive in my computer has been formatted also letter for the drive letter disappears any every reboot
 
Thanks for reply the drive is sata wd 2tb drive have chck drive for errors using wd test program .all conections are good ,formats ok ,did long format ,disk mangement tells there a drive ,if you had a letter it appears in my computer ,if reboot lose the letter and does not show in my pc ideas ?
 
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