Problems joining friends

Supposedly our devises are compatible but it doesn't work properly right now. I can only join my friends on the condition that the world in new and I haven't ever been in it before. I have checked my firewall and Minecraft is allowed through and so are all the platforms that it requires. My network connection is good I have even tried a wired connection, and rebooting the game and my pc, and she has also rebooted her device as well.