When I try to reply to my friends that message me while I am in game I ALWAYS get this message "ERROR: This person is not on your friend list" or something like that. It's been happening constantly. When I reply I do /r and when I type their name appears. I've tried manually typing /r *friend's name* but I always get the message telling me that they are not in my friend's list... How do I fix this? Please help.

*when I message my friends they can reply back to me when they're in game, why does it not work for me? :/

help please anyone