In Minecraft 1.8.8, the .json file for block models could have comments, either in the form of //comment or /comment/
As of the 1.9 snapshot, if either of those are anywhere in the file, the block will not render in the game.
I am assuming (and hoping) that this is a bug because comments really help keep the files organized.
Please attach the resource pack with comments and game output console after reloading the resource pack