Problem with my Raid menu?

Hello,

I am rather new to the game so this might not be any bug and just a mistake I am making but I was trying to sign up for raid and I kept getting error.

To explain simple, the way I was trying to sign up (list my name) for raid was - Opening Social Menu (O) ----> Pressing on "Raid" Tab -----> Open Raid Browser. Then I get the menu to select which raid I want to go queue for and so I select "Black Temple" for example then I click "List my name" and in the chat bar I recieve message saying "Internal LFG Error".

Can someone explain me why is this happening and if needed I will show you some snapshots to make it more clear.
Awaiting responce asap.
Cheers!