I want to just chime in here.

For one rank up, it requires you to complete Darkhold. I see that some of you have done that. The rank up directly after requires you get the quest for Amdapor Keep from the same person. This quest will only appear after you did the Darkhold quest *AND* completed the entire Main Scenario. I also believe for the rank up itself, you will need to complete the Hunting Log 2 for the GC. But basically, complete Darkhold+Main Scenari. (I will add that I unlocked Ifrit Hard before even checking the GC, but I haven't done Ifrit hard, so you may need to follow that and attune to the aetheryte, but I'm not sure about that)