When does the mine dungeon become available for this quest?

I'm on my first NG+ Ch4, I've met all the requirements and still I don't trigger an event to unlock the map.

*(req. Wil lvl50, Aht, Suina, Crayl, Melo, Saerav recruited)*
Done all of them, unless every character listed needs to be lvl 50 besides Wil...

You know it's in Yuidora Mine, right?

Yes, I know.

I meant to say that I have fulfilled the requirements but nothing happens.

Do I need to be in a further chapter for it trigger?

Just reached Ch5 and got a letter telling me that I failed the quest, even though Wil is almost 70 now and everyone else close to 60.

I don't understand how could I fail since I recruited everyone as soon as I can, leaving no quest behind after advancing each chapter.

Chapter 5? Then, you ignored some event. In chapter 3, a new quest (quest 85) should become available to you and that quest lets you enter the new dungeon.

By the way, the recruited characters were cloned units?

The recruited characters were clones until I "recruited" them through events.

I don't think I ignored an event 'coz I did everything before advancing. It just didn't show up.

The only thing I recall was that my Wil wasn't lvl 50 when I got the quest, but on that same chapter I got him into 50.

Are you sure? Don't forget that some characters join you as guests, and they are not "recruited" in your party. If not that, maybe this is it.

If it isn't either, then I dunno...

When you say you recruited everyone, do you mean everyone on the list of the quest requirements or everyone available in the game? There are only two characters whose join quests are failed by starting chapter 5 (assuming that part of the list is accurate): Uya (and by extension, Kohakuren) and Sharty. Uya is on the list, so I assume you recruited him, but did you recruit Sharty? That's pretty much the only way I can think of for you to have failed the quest upon advancing to chapter 5.

I figured it out. Just like LonerAoshi said, I failed to recruit Sharty which is not in the list 'coz I forgot to synthesize the Alluring Perfume. I don't know why but everytime I looked into Info>Quests and saw the Sharty quest, I thought that it triggered on a further chapter. Also the requirement list didn't list her.

I had a previous save so everything is ok now.

Thank you ELFail and LonerAoshi for your input.