Tellraw command “not reading the t!”

I tried to enter this command:

/tellraw @a Herobrine joined the game

But the error message says ”Unknown command ellraw”

So it seems as if it is not reading the t!
/tp is working

/ tellraw @a Herobrine joined the game

is not working

Why is the game not reading the t in the tellraw command?

I am playing on Windows 10 ( bedrock edition)

/tellraw @a {"rawtext":[{"text":"Herobrine joined the game"}]}