MLB The Show 21 has been updated to version 1.18 today by Sony San Diego Studio. You can find out the complete patch notes for this update from here.
According to the official Twitter account, there were connectivity issues with the game that continued to happen throughout the day. As a result, the servers were down for an extended period of time and a new patch was released to fix the issue. The patch is out now, and the update is live on both PlayStation and Xbox consoles.
MLB The Show 21 Update 1.18 Patch Notes
We will be deploying Game Update 18 soon. This should address the connectivity issues and there are no other changes to note.