Fix #1: Use a non-child account. The most common reason why many people are unable to join a game and encounter the Roblox error code 103 is an issue with their account.

As mentioned, this seems to be an issue that primarily targets Xbox One users. If the above steps fail, be sure to reach out to Roblox’s support team for more help.

Make a new ROBLOX Account without Age Restriction. Allow Content from other people. Forward the Ports used by Roblox. Perform a Power Cycling Procedure. Uninstall, then Reinstall Roblox. Let us ...

Basic Reinstall: Uninstall Roblox through your control panel (or Apps settings) and then download and install a fresh copy from the Roblox website. This is your first line of defense.