Your stream key is a hidden password that is used to authenticate with DLive when starting your live stream. Your stream key should never be shared with other users unless you want them to "Go Live" on your own channel.
Unfortunately, resetting your Stream Key is not possible with DLive without a member of staff doing it for you.
The option in your streamer dashboard to "Regenerate Server URL" just reveals the existing RTMP url and stream key.
To request a new stream key, you first need to contact the DLive Team by visiting their help site and clicking "Submit a Request" (at the top right).
You can also raise a support ticket by emailing: [email protected]