A water emergency prompted the mayor of Capri to order a halt to the arrival of tourists

AP:

The emergency was caused by a failure in the mainland's water system that provides vital supplies to the world-known island.

...

Ferries and hydrofoils that had already departed for Capri were contacted by radio by the maritime authorities, which ordered their return to port and disembarkation of passengers.

Later last night:

On Saturday evening, however, the island’s mayor Paolo Falco said the ban had been “revoked” after a technical issue preventing the arrival of water from the mainland had been fixed.