[2020] I can get to lobby but i cant start apex game

Hi, can you ensure that cross-play is enabled?

You can toggle this on within the XBox system settings. 

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 Customise
5. Click on Communications and Multiplayer
6. Change "You can play with people outside of Xbox Live" to unblock.

Sorry I have no idea. Maybe it was disabled for a different cross-play game, or was turned off by a cautious parent or sibling, if that's a factor?