Is the Officer bound to you?
I found the issue... they are actually both "Liberated Borg Engineering Officers". I did not realize they were both engineering. So it only lets me have one of them. I guess if I chose 1 Borg Science and another Borg Engineering, it would let me. But since they are the same officer and same field, I can't use them both.
The one being used (Seven of Nine) is currently an active Bridge Officer, Lt. level. The one in my inventory is just in my inventory. Not sure if that means it's bound to my character or not? Just when I open up my inventory, the second one is there and it doesn't let me use it.