Does anyone know why tickets are not available on Trenitalia 9287 from Paris to Milan between May 5th and May 11th?
I tried it for May 5 on the Trenitalia website, and it says there’s one at 3:11 (and several different trains before that). Did you set the earliest time you might want to go? If not, that might account for your lack of results, taking into account the time difference between where you are and Paris.
I will guess that there is a major repair project planned in the Frejus Rail Tunnel that the direct train uses. I see that they a currently working on a new Base Tunnel to replace it. You can get from Paris to Milan with a single connection in either Lausanne or Zurich.
It's almost 7 hours by train Paris-Milan.
Vueling, Ryanair and EasyJet fly the route in 90 minutes with airfares starting at around $66. Many, many non-stops are available daily.