PiedThePiper, I am not sure if I understand what you mean. I believe you are saying that the server wasn't showing SD card #2, even though it was installed. If this is the case then it is likely that within the BIOS the SD cards is set to Disabled, which allows only SD 1 to function Let me know what you see.
It currently shows no SD2, even though it is inserted  correctly and before the change it said SD2 had failed, I have replaced SD card 2 and the enclosure bit too as they were supplied by Dell  Any ideas? 
replaced SD card in r720