USually what happens is that if someone got it first, the ability to interact with the rope remains and you can still initiate the rope but the interaction sequence circle logo gets cut off at the point when the first person finishes his interaction successfully. then you interaction icon basically cancels out automatically and you’re active again in the game which means you need to grab another rope.
So, It means you did not successfully exfiled to the chopper, you must see the animation sequence of going up there.
IMHO, they should redesign it so that it is apparent that it is not available. Simple as making it blink while it is being interacted with.