the invite a friend button will not show up

I have been playing Minecraft: Windows 10 Edition with a friend. For the past week I have been clicking a button that says, "Invite Friends". The way you pull it up is: Once on the world chosen, push "esc" on your keyboard. This button has been working for the past week with no problems what so ever. Today, I logged on to play with the same friend and no matter what I did, that "Invite Friends" button would not show up!!
Please help with this issue!