Thank you for the additional information.  Power down the server, open the case and reseat the ISDSM  card reader and reseat cards as well.   Then power up and check the F2 bios under integrated devices to see if the reader is visible.   If not, then contact your support channel either by phone or chat for further troubleshooting and possible replacement.  Regards,
SD Card Reader is no longer under 'Integrated Devices' on Poweredge R420. I did a firmware update, and it was running Xenserver for some time. Xenserver install also does not detect and drives. I reset BIOS to default. Warranty?
SD Card Reader No Longer in BIOS