Train Booking Rail travel in France

If you book a standard full fare ticket, then you can exchange it for one for a later train. If you book a discount fare ticket for a train that requires a seat reservation (like TGVs), your ticket will be no good if you miss that train. You'll eat the cost of the ticket and you'll have to buy a new full fare ticket for a later train. Tickets for regional trains are good for any train on the route covered by the ticket.

To put it another way and I am not as familiar with the French trains because it has been a few years. But this is fairly universal. IF the train requires a seat reservation and your ticket lists a seat and car number AND is a fully fare ticket then you have been between an hour and 90 mins depending on the train system to get a new reservation at a ticket window. IF a discount ticket, most likely it is dead but will depend on the limitations on that ticket at time of purchase. An exception is made if the train was late in arriving for the connection. If the train is mixed (seat reservations and non reservations) and you ticket is an open ticket then you can catch the next train provided it is the same type of train.