Hi there, 

My son has been playing the Java Windows 10 version in multiplayer but cannot access the chat or command bar functions. However, these functions do work in single player mode. We have read that changing the chat settings in 'Options' to 'shown' should normally fix this problem. However, this is not solving the problem for us now. We have disconnected and reconnected to Minecraft to see if that solves the problem too, but nothing is different. Is there another solution to this issue? Strange that all is fine in single player mode! We would be very grateful for your assistance. Thank you and best wishes.