I already used the 3 terminals to approve access to the aminframe but the door still says "Requires key". What else am i missing?

Have you run into the Master Brain yet? This is basically a Robobrain, which you kill, then must activate its body, to "shut down" all security, which unlocks the door for you.

I shut down the security too. No dice.

Also the wiki only mentions that the 3 terminals are needed and the security shut down is for something seperate.

There is a bug there that sometimes prevents people from opening the door even though they've done all they're supposed to do. I wouldn't worry about it though because all the information you get from it you also get once you get inside the Citadel and speak to one of the BoS.

there is an exploit to counter that bug just go into the room on the floor thats below the floor where the locked door is. the room where you can see the mainframe. walk in the door , go straight till you hit the wall , turn and face the wall to your left, walk to the wall and jump up on the metal pipe. from the metal pipe you can jump up and over to the mainfram , while your in the air as soon as you see that your able to interact with it push E and wa la . It will take a few tries but it is possible

Or i could just unlock the door with the console...