I'm experiencing the same issue.
I'm on Windows 10, my son is on Xbox One X, both latest Minecraft editions (bedrock).
We're 'friends' via Xbox App.
Visible online via Xbox app on Win10.
When he plays MC on Xbox, he shows up as being online playing Minecraft.
I start MC on PC, but can't invite him to any featured servers (such as Lifeboat, etc) and he can't invite me.
I thought the 2 versions / platforms were supposed to allow cross platform play?
We can play together on LAN games, however.