The first thing you have to do is verify that your friends are connected> make sure to also activate Crossplay if you are on a platform other than your friend's> press the menu button> access Friends> and select your friend or send the request to befriend in the Requests section, writing your username.
After inviting him to an exhibition game, you can start the game.
For Diamond Dynasty mode, you can play against friends from the Diamond Dynasty menu.
To start an online game much faster you will have to press the profile icon> press R1 or RB according to your platform to access "My profile"> click on the Friends button to access the list of your friends and send requests to then start the game.
That's all you need to know about how to invite friends on MLB The Show 21, so now that you know, we hope you get to enjoy a good time playing cross-game with your friends.