BDO Codex

I followed the quest line up to the point where I was told to give the key to the ruins to someone I trust. I gave the key to Edan, and he gave me a fake key. However after I received it, there were no follow up quests. I googled what to do with it and it said to give it to one of the princes, but there was no quest or chat option. I tried all the other royal family members and again no option to give the key. I checked the black spirit and there’s nothing available for the main questline. I tried deleting the key, to get a new one from Edan, hoping it would fix the quest, but now I can’t get another key. I don’t know what to do, I can’t continue the story because of this and it’s really annoying.

Try to contact the game's support about it. Maybe they can reset your quest.

How do I do that?

You can send a ticket to the support. For NA/EU version of the game it could be done here:
https://blackdesert.zendesk.com/hc/en-us/requests/new