There are not currently any low-cost airline routes between Paris (Orly) and Milan (Orio al Serio) with MyAir.
Instead you could try browsing budget flights between Paris (Orly) and Milan (Orio al Serio) with all airlines.
Another option would be to try browsing all low-cost airline routes to Milan (Orio al Serio) or all budget routes from Paris (Orly).
In the meantime, this error has been logged.