I have a similar issue.
several Dell R720xd servers with a Gigabit 4P I350-t Adapter, and i can't get the firmware updated to 16.5.20
I am using the latest SUU dvd, from witin the lifecycle controller. The error message in the lifecycle controller is:
SUP0520: Unable to update the Intel(R) Gigabit 4P I350-t Adapter firmware to version 16.5.20.
Any suggestions on how to get the firmware updated? The servers have ESXi6 as OS.
