i have recruited the lati's and unlocked sky blue plains but the wish cave event won't start whats going on?

You need Surf too. Do you have Surf? If not, its in the Solar Cave 40f. You need a key and I think a water crossing pokemon.

i already have that

Well, the only criteria is unlock Sky Blue Plains, get Surf, clear Pitfall Valley, and talk to medicham and ekans in the wishcash pond area. I don't know what esle to tell you.

after you talk to them once you got the chain started. go see them everyday and they'll say more stuff. days they aren't there check the post. one day ekans will be posting. take the mission, save medicham, and you can go to wish cave and have the stone.

If you haven't cleared out your mailbox then you're gonna want to do that.

You get the mail to get the Sky Blue Plains as a reward in your mailbox.