Code leaf means you're having connectivity issues to EA servers. This error should have been fixed in 2019, but may still happen.
Unfortunately, there is nothing you can do to fix the issue on your side. You need to wait for EA to deploy a hotfix on their servers, which would solve the issue. Still, you may restart your computer/console and your router.. it may solve the issue !
According to EA support, code leaf happens when the server never answered us when we asked if it could connect. […] The vast majority of players reporting the error are getting code:leaf. This means the backend created a match, our servers successfully talked to one another, we sent users there, and the player never got an answer from that new server.