The question you asked before was hidden because it should have been asked on PokeBase, not Meta (you were right the first time). The way you worded it made it sound like you were asking "Why isn't my Gible evolving?" and not "The info on Gible is wrong".
By the way, I had a look around and Bulbapedia and Serebii both say 24. So maybe Gible holds an Everstone, you caught Gible over level 24 (just level it up again and it will evolve if this is the case), or you are pressing B while it is trying to evolve?