/tellraw with clickEvent not working [java] 1.21.8

Hey, I came back on a minecraft map where I had clicevents but they don't work (now on 1.21.8 on java).
So I looked on the internet but I can't solve this...

I tried this (found on reddit)

/tellraw u/a {"text":"block","clickEvent":{"action":"run_command","value":"/tellraw @a Hey"}}

But it is impossible to click on the message and I can't solve this at all. It doesn't detect at all that it's a message that you can click on...