If you can’t connect your Discord account to Cornix and receive the error message from Discord:
"Your message could not be delivered. This is usually because you don't share a server with the recipient..."
This usually happens because your Discord account is not connected to any Discord group that is integrated with Cornix.
To connect your Discord account, make sure you first join a Discord group that is integrated with Cornix (as mentioned on this article). Once you are part of an integrated group, you will be able to successfully connect your Discord account to Cornix.