There are not currently any low-cost airline routes between Paris (Charles de Gaulle) and Venice (Marco Polo) with Vueling.
Instead you could try browsing budget flights between Paris (Charles de Gaulle) and Venice (Marco Polo) with all airlines.
Another option would be to try browsing all low-cost airline routes to Venice (Marco Polo) or all budget routes from Paris (Charles de Gaulle).
In the meantime, this error has been logged.