Friends online within game do not appear in the Joinable Friends list

I play Minecraft for Windows 10. My nephew and niece play it on XBox One. I am in the UK and they are in the UAE.  When I purchased the game I was able to play with them for 2 days. After a week I can see them as friends online (green dot) from within Minecraft but they do not appear on the Joinable friends list. I have checked all privacy and Xbox settings for me and them by adding them in my family group. The settings are all correct. Also the invites don't work as well. I cannot receive their invites and they see my invites but when they click nothing happens.

Please see the issue in the screenshot compilation. My gamertag is the one starting with M and my nephew's gametag is the one starting with A.