how to get payback for TGV that been cancelled

Where did you book it? If Interrail, contact Interrail customer support.

In such situations, you should cancel the reservations before departure or 30 minutes after departure directly on the vendor’s site. This is easier as to obtain later a refund. It should also be possible to make it on vending machines of the SNCF, but you receive a voucher and not the money.

You can also exchange the reservations on a vending machine, but you have to pay a surcharge is the new train is more expensive as the old one. In case of problems, an exchange is probably free.

This is the mail I get when I was traveling and ha e o ly my phone with me, 

And I book it via Interrail.

Hello,

Your 5040 train on 26/07/2024 to BORDEAUX-SAINT-JEAN has had to be cancelled.

Within 2 days of the departure date shown on your ticket, you may:
 

1.Exchange your ticket free of charge, keeping the same departure and arrival stations, postponing your travel to a date up to and including 02/08/2024.
 

- Either by clicking on this link
- Or via your usual sales channel.

2.Receive a refund for your ticket by cancelling it through your usual sales channel.

And don't worry, if you incur any charges when exchanging or cancelling your ticket, they will be refunded. Simply submit your request to our claims department by clicking here.
 

We apologise for the inconvenience,

The SNCF Voyageurs team