Weird ‘theme update’ error [duplicate]

For the details link you need to set Details URI: in the header of your theme’s style.css

Your Theme Name: also set there should create the slug the WordPress uses to query the wordpress.org theme repository for updates via the Update API. (I know for certain having tested it that slugs for plugins are created from the plugin name, I think it will be the same for themes but I haven’t tested it specifically.)