RuneScape has updated the game, causing players to be stuck with "press enter to chat." This RuneScape guide will explain how to toggle it off.
The game added a new button to the interface with which to toggle chat on and off. Prior to April 28, 2014, RuneScape players had to press enter if they had their action bar or an interface open and did not have to if that was closed. Now it's always on or always off, depending on the button.
The toggle chat on/off button is located next to the premium membership star, online status, and report an issue buttons. For my interface, using old school, it is above and right side of the chat area.
RuneScape players simply need to press this button to get rid of the "press enter to chat" and can toggle it back on with one click when they need to use their action bar.