Certain Pokemon are coded to never be shiny. But I don't think Lati@s is one of them. It may just be bad luck. What sort of range of frames are you getting, and how many times have you tried?
I don't say it's coded to be not shiny. But not to be shiny and have that spread I guess.
First spread was Frame 42, second one 576. And couldn't hit both for life.
41,43,44, 573,575 but never the target frame cause it sorta makes after you leave the house jump the frame to a point where it's not possible to hit the target frame. no matter what you do.
I tried about 166 times I guess. And I'm not bad in RNGing... (check my thread)