The chat window should appear when you press Enter. If it doesn't, it means the window has been moved out of view. This can happen if you accidentally click and drag the window, or if you recently played on a very high resolution. The chat window's position is saved from game to game, so follow these steps to reset it to default:
- Open C:\Riot Games\League of Legends\Config\PersistedSettings.json
- Find the Chat section, which should look like this:
- Change the "value" field under "ChatX" and "ChatY" to 0 to reset the location.
LoL will create a configuration file in the "hud" folder with your settings. Navigate into this folder and make sure that the file has been created. It should be named after your resolution, and you should be able to open it with Notepad or another text editor.
If you've followed these steps and you still can't see your chat window, please send us a ticket and we'll investigate further.