Many thanks for reaching out to the Mellanox Community.
Please check if reburning your firmware when the card is booted in the Livefish mode, resolve your issue. If this does not resolve the issue, the card is dead.
For booting you card into Livefish mode, please follow the instructions in the MFT (Mellanox Firmware Tools) User Manual ( http://www.mellanox.com/related-docs/MFT/MFT_user_manual_4_10_0.pdf ), Appendix C: "Booting HCA Device in Livefish Mode".
For correctly burning the firmware in this mode, please use the following command:
# flint -d <device> -i <firmware bin file> -nofs -guid <card guid> burn GUID can be found on the HCA sticker.
# flint -d /dev/mst/mt26428_pciconf0 -i MNPH29C-XTR.bin -nofs –guid 0002C903000B6D1C burn
After successful burning the firmware, please reboot the card in Normal mode.
~Mellanox Technical Support