Can't write into the chat (Mac)

[Matoyomhun]

Hello,

First of all sorry for the bad english, I'm french. I am experiencing quiet a problematic issue: since this afternoon I can't write in the chat anymore (which is making my gaming experience quiet limited since LOTRO is an MMORPG).
I guess I used a keyboard shortcut by mistake, but I cannot find which one via the settings.
I am playing on Mac, and I have never changed this keyboard shortcut.
Can you help me out please?

Thank you in advance,

Harendir, from Sirannon