When enchanting the tool, specifically diamond and iron pick; with that of forntuna III and IV he does not drop or fails to obtain the specifics of this enchantment.

Save my levels until 30 to be able to get the enchantment of Fortuna II, I used an iron spike so that it would give me more diamonds but they gave me the same ones that were seen, it was there that I again enchanted an iron spike but of Fortune IV and the result was the same, I tried again with a diamond pickaxe and it was the same as if the enchantment didn't work.