The CD keys in use is usually because the server hasn’t dropped your last game because of a sudden disconnect. It resets itself eventually.
Your next login failed because of a possible restriction. They are caused by several things.
Your Starlink connection might be seen by the server as a business IP address which is forbidden on classic Diablo 2 servers. (I’m assuming you are playing classic, not the new version.)
You can also be restricted when using a VPN. You can see a full listing here:
In addition, you can submit a ticket to support for assistance. They can see the cause of it usually.
The SUPPORT link is at the top of this page on the right side next to your name.