kyrne/websocket has actually been open-sourced and is hosted on Packagist.
Double-check you configured the Flarum.org repository. Create a new Flarum.org token if needed and follow the "Instructions" guide (the button is visible on your screenshot).
If you have never updated the private repositories since Extiverse was renamed to Flarum.org, this action is required. You can remove the line for Extiverse in composer.json afterwards.
Because of the different messages I assume it's the correct location, but is test really your Flarum folder? (the one that contains config.php and composer.json) Make sure you navigate to the correct location before running the command to add the repository and then run the require command(s).
