I can't see my friends

Hi my name is Javier, and I have an issue with Minecraft P.E I'm not able to see my friends and play with them it appears me in the XBOX app that they are online end when I go to Minecraft it says that my friends are currently not playing Minecraft then I go back into XBOX app and it says that Tehran are online. This issue started appearing me this morning when I saw that my friends where playing Minecraft I went into Minecraft and I saw that no one where playing so I hope you can resolve this issue.