When I invite friends to play my map made in UEFN and published, they can't

They aren’t. But I’ve tried both ways, public island (Look the capture) and the private one.

  1. On the one hand I want to have a public island working were poeple can enter (by the moment I couldn’t do it)
  2. On the other hand I want to have a private island for my comunity, but not all of the are friends. But i would like to have it private for my comunity.

I haven’t been able to do it in any way but not sure why.

Is it possible to have a custom server for example if i want to have it in amazon web service or my own PC?

Hope you can answer all my questions, thank you!