This from the Man in Seat 61
Paris-Milan TGVs stopped by landslide...
Paris-Turin-Milan TGVs are cancelled until (probably) 15 August due to a mudslide near Modane blocking the line. SNCF are offering postponement or refunds. What people really want is diversion, but this means new tickets! The route to Milan via Lausanne or Basel is open.
See here: https://www.seat61.com/news.htm
Modane is at the French end of the main rail tunnel under the Alps between France and Italy (Fréjus tunnel)
I can't find anything else in English, just angry news reports in French.
For example: https://www.tdg.ch/monde/ligne-tgv-franceitalie-via-modane-coupee/story/23627797
Says "unusable for many weeks".
And this one with a photo: https://www.ledauphine.com/savoie/2019/07/11/alpes-la-desserte-paris-milan-se-desserre-un-petit-peu-sncf-train-boue-modane-saint-michel-de-maurienne-rail-transport