BO4 keeps going back to home screen

I would check Activision support channels for details on the status of the beta services. It's pre-release software, so it's not uncommon for the game, app, services, or network to experience some issues. You can also try a full power cycle of your console,
by pressing the Xbox button on the console hardware for 10 seconds until it powers down, and then wait another 10 seconds before powering it back up.

I see you tried reinstalling the app. Did you clear the cache and then restart the console before reinstalling it?

Actually, Yes. My grandson just informed me he was getting updates this morning and I turned off everything before leaving for work.

Guess that'll each me to ask and him to inform me!!

Many thanks!

Hi
DragonHunter307,

Thank you for contacting the Xbox Forum. This is an issue i have encountered many times myself. The first option is always to go with a Power Cycle of your Xbox. Turn off console by holding down the Xbox button on your console until it turns off. Then unplug
your console from the Power socket in the wall and wait 10 secs. Then plug it back in and restart your Xbox.

If by chance this still causes Fortnite to go back to home screen instead of loading your next suggestion is to do a resart on the game. The easiest way to do this is to open up another game and let that game fully load and then go back into Fortnite.

Please let me know if this helps you.

Thank you

Further to the above suggestions, if some of the easier methods don't work you can try to reinstall the game fresh from the store. There is a chance your console was powered down during an update which can cause issues with the build.