You either provided a wrong password or cancelled the authorization. Furthermore there could also be a technical reason for this error if you haven't seen a password dialog: your desktop environment doesn't provide a PolicyKit session agent.
Thug thu seachad facal-faire cearr no sguir thu dhen dearbhadh. Mur am faca tu còmhraidh facail-fhaire, dh'fhaoidte gu bheil adhbhar teicnigeach ann: chan eil àrainneachd an deasg agad a' solar àidseant seisean PolicyKit.