Getting the private restaurant room in HHP

[EmGee]

How do you do it? Nookipedia says you need 3 pairs of roommates and then Lottie will suggest it, but I've set up 3 pairs and it hasn't happened, so what am I missing from the method?

 

[~Kilza~]

You need to have experienced the DJ KK concert in addition to having the 3 pairs of roommates in order to unlock the private room in the Restaurant. If you have 3 pairs of roommates before the DJ KK concert then experience the concert, you'll need an new pair of roommates to unlock it. (source)