If "doesn't see" means the system setup does not detect the drive, it likely is not connected to the system board.  SSDs are appreciably slimmer than the 9.5 mm drives this system was designed to handle.  Use a spacer (example below) to allow the slimmer SSD to connect to the system board. [URL]  
I want to upgrade my D620 to make use of a spare SSD. It currently has a 40gb spinning disk which works fine running XP. I put the SSD, and the BIOS doesn't see it. I tried a different SSD, a Kingston A400 (which some sites recommend as a compatible upgrade) and it doesn't see that either. I have formatted them to NTFS, made partitions active, still nothing. Any thoughts? 
Latitude D620 BIOS does not see a 120gb SSD