Tellraw and Title command doesn't work

Hi, the command tellraw and title don't work, I've tried:

/tellraw @a {text:"Hello"}

it says: injavild json. So i tried:

/tellraw @a hello

it don't work, also says problem with Jsons, on all of my command blocks, which the tellraw and title command always work before, don't work anymore. IT's there since the snapshot. Please fix it.