Did you connect the 4-pin IPMB cable? Please follow the instructions in S5500 based pedestal systems backplane and RAID Controller cabling guide. Also take note that you'll need to run the correct .nsh file based on which HSBP connector you're using.
Yes, indeed as Edward stated above, you will need to have the ipmb cable connected correctly.
Make sure you are not connecting the ipmb cable to the ipmb connector on the board. This is something different.
There is no need to have ses or sgpio cable connected connected.
And here is a small guide how to update the firmware thru efi.
All the best,