Hello, I am writing with an inquiry as it is with the secondary market, I bought a diablo 2 version on the CDs I have CD-keys in this, but they were used on the battel net site, the owner does not remember the login. What then can I do? Formally, I have CD-key labeled CDs but I can’t play them
Get your money back.
Once a license key is bound to the Battlenet account it is considered used. Battlenet accounts must be created in the real name of the player and they can not be transferred or sold. That gets the account banned. So, even if the former game owner remembered the login, selling you the account is a violation of the EULA.
Further, Blizzard bans keys that are used for botting, cheating, or other nefarious activity.
NEVER buy a used key for a game. You can buy the box and media if you like collecting such things for display on a shelf, but keys are a very risky thing to try to buy. Always buy directly from the game maker or a valid retail store where you have some consumer protections.