Hmm, just to clarify, is your old YouTube channel created before May 2009? If yes, we've automatically connected it to a Brand Account. You'll need to get access to it in able to delete your channel. Follow the steps here: https://yt.be/help/ZCXd Keep us posted.
These steps may help you regain access to your account: https://yt.be/help/nr5L . We recommend doing this from a known device or browser that was typically used to access the account. Here are more tips to help you through the process: https://yt.be/help/KyrL Hope this helps.