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