I confirm the Intel® Server Board S5000VSA is not among the supported boards for the Intel® RAID Controller RS2WC080 (click here). This explains as to why your RAID controller card does not detect any of the drives in the backplane. For a list of validated hardware RAID controllers for the board in question, please, refer to the tested hardware and operating system .pdf file found here.
Finally, I confirm there is no 3 Tb. drive size support on the Intel® Server Board S5000VSA as you indicated.
Are you able to test any drive connected to this cable and bypass the backplane. This would confirm if there is communication between the RAID controller and the drives when using this cable. By the way, was this cable provided by Intel?