For those who bought tickets through TicketOne, there is a process to follow in order to get your money back.
https://www.ticketone.it/campaign/en/covid-19/
If you order on line, look for the heading TICKETS TO CANCELLED EVENT TICKETONE.IT OR CALL CENTER. Click where it says click here . That will lead you to a form to fill out. It's in Italian, but you can use Google translator or any other translator to figure out what it says.
We're lucky because I believe some concerts between March and May only allow people to get vouchers for future concerts, but we get our money back.