I was in an instance and I couldn’t reply to anything or anyone on my pc. The only way I know how to access the chat menu is by bringing up a menu and blocking out my entire screen. I know that doesn’t work during battle. Worse I can’t toggle to the Instance tab or League tab. F4 does literally nothing for me. Does it make a difference on my computer model/type being a Lenovo?
I've played the game on a Lenovo/Dell wSteam and without on various Laptops and PCs. I've seen nothing where the chat box will not come up (in-game chat...not sure if you are referring to a discord or other chat...assuming in-game), and the only time I've seen one that takes the whole screen is when I accidentally super sized it. Open the chat box and grab the upper right corner of the box with your mouse cursor and see if you can drag it down to 'normal' size. If you are using a PS4 style controller, press Triangle and use the right stick to control the size and shape (as memory serves). If you are just saying you can't get the chat to come up, I think the default key is / or Enter (I mostly use controller), or again, on PS4 style controller, press the large middle button. F4 brings up one of the social menus I think...again I don't use KB much.
On ps4 press the touch pad in middle of controller, to resize chat window press touch pad to activate chat then press and hold triangle then use right joystick to resize, you can also just tap triangle and it will resize to a default size but to make it bigger than that you have to do the holding triangle part.
Yeah as everyone has already said it's either / or enter for in game chat. Also, after you hit enter, you can then use your mouse to select which chat channel you want to be chatting in as far as the tabs go. If you want to add or remove specific channels, this is done in the in game settings.