Minecraft/Xbox Live not working when Content Restrictions are enabled

We recently had to enable Content Restrictions on my son's iPad, but now he cannot sign in to his Xbox Live account in Minecraft. 

The iPad is currently running iOS version 12.3.1

In the Settings app on the iPad I go into 'Screen Time -> Content & Privacy Restrictions -> Content Restrictions -> Web Content'

We set the Web Content to 'Allowed Websites Only' 

But now when we go into Minecraft on the iPad and try to sign in to the Xbox Live account we get the message "Sorry, something went wrong. Give it another try, or try on Xbox.com"

If we change the Web Content setting to 'Unrestricted Access', or 'Limit Adult Websites', Minecraft allows us to sign into Xbox Live. 

We have tried adding https://xbox.com to the list of allowed websites, but that isn't working. What address/domain do we need to list that will allow Minecraft/Xbox Live to work within iOS content restrictions?

FYI - I've tried posting this question on Microsoft community forum (https://answers.microsoft.com/en-us/xbox/forum/xba_modi/sorry-something-went-wrong-give-it-another-try-or/f36aaa4f-e30d-466f-a49e-0d80a8f7a867?tm=1561911439816), but no help so far.