Somehow, I was able to complete the quest: YOU'LL KNOW WHEN IT HAPPENS before I did the quest FOR THE REPUBLIC, PART 2. Because I did the quests out of order, Colonel Moore wants me to talk to the Ranger about how to protect the President. The problem though since the President has already been saved, the Ranger is not in the Visitor's Center. He's outside on the Observation Deck, and his character doesn't talk to me. If I can't figure out a way to complete this quest, I've just wasted 40 hours of my time.

Do any of you guys have any solutions?
Maybe Obsidian will figure out a way to fix their crap game.

I have this exact issue

I have the same issue except I didn't do YOU'LL KNOW WHEN IT HAPPENS until I got the FOR THE REPUBLIC, PART 2 quest. Thinking I could avoid the paradox problems by doing them at the same time, thus only having to save the president once. Unfortunately this didn't really solve anything... I saved the president and YKWIH was completed but FTRP2 has all of the objectives complete but whenever I try to talk to any of the NCR people they just say wtf are you not protecting the president. So I don't really know what to do at this point except wait until there is an update. sigh...