Xbox Live Multiplayer. Disable Family Settings

You can block access to LIVE from the family settings.

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Guide button, Settings blade and then Family Settings.

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Change the setting to blocked and create the passcode.

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Now every time you start your console, or sign-in you wont be able to access LIVE. Just disable the option in family settings when you want to play on LIVE again.

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PVP is not allowed

because of your xbox live setting ,mulity people gaming function is disabled ,please comfirm you have the correct xbox live account and comfirm your xbox live account had already turn off the family setting;

Please check to see if cross-play is enabled under the Xbox Privacy settings for that particular account In addition to the Child Account Family Settings, there's another place where you can enable/disable cross-play as well. To see if it's enabled follow the steps below:

1. Go to your Xbox settings
   
2. Scroll to Account and click on Privacy and Online Safety
   
3. Click on Xbox Live Privacy
   
4. Click on View Details and Customize
   
5. Click on Communications and Multiplayer
   
6. Change "You can play with people outside of Xbox Live" to unblock.
   

A child account has multiplayer play disabled by default, so you'll need to authorise him to do it. Go into Settings on your Xbox (when logged into a parent account) then into Account > Family settings and choose his profile. There you'll be able to control
what he's able to access online.

Is there a family settings enabled? Try disabling it from the Settings, Account and then Family settings