@MojangSupport friend can't connect to me on Bedrock. I play Win10 Edition. I click Play, <world name>, and the world opens. They can see it listed but joining leads to "can't connect" error. Why is there no error log? Trying to find out WHY they can't connect is so frustrating.

For help with Realms, check out: msft.it/6011bG8Tb for troubleshooting options. ^FF

It's not a realm, it's an Xbox Live hosted session I believe. You host a sp world on bedrock online and friends can join it over the Xbox live network. No realms involved.