Having problems trying to start a Realms subscription with Minecraft Windows 10 Edition

I keep trying to start my trial/pay for a Realms subscription, but it keeps giving an error saying:

You need permission

You cannot play on Realms because of how your Xbox Live account is set up. This can be changed in your privacy and online safety settings on Xbox.com

Fine. Changed my settings. Allow everything. Still getting the same message. What am I doing wrong??

Solution 1:

I've just done this for my two kids - it took a while to work out!

I set all the options for Xbox Live for the two accounts to 'Allow Friends'. That wasn't enough. I also had to go to the Xbox One page and check 'Join Multiplayer Games'. Then it worked.

Note that there is a short delay when changing settings online. This may give the impression that it hasn't worked when actually the game simply hasn't rechecked permissions.