I looked at the picture of your subpanel, it appears as though there are only three conductors coming out of that conduit. You need four. You also needed to have bonded the rebar in the slab (called a UFER ground).
For my education only. When I did the power to my shop it was from the meter base and I was given the option to use ground rods or a UFER ground connected to a minium of 20' of rebar in the floor. Are you saying that a UFER is required by your jurisdiction?
BTW I used two ground rods and nothing to the steel in the slab and was ok'ed by the county.
lg
no neat sig line
