Buying rail tickets for travel in France

Depending upon your destination, schedules may or may not be available, check here:

https://www.sncf-connect.com/

If schedules are not yet available, the SNCF will send you an email, notifying you when they will be.

If you have problems with the above site, try here:

https://www.thetrainline.com/en-us

Definitely purchase tickets on advance for best fare and to guarantee availability.

Here are a few sites to get you started.

The Man in Seat 61 is the guru of train travel in Europe. There is a wealth of information on his website.

SNCF is the French rail company.

The Trainline is a company that sells tickets for SNCF. Useful if you have a problem with the SNCF website or app accepting your credit card.

https://www.thetrainline.com is easier to use in my opinion.

There are specific trains I want us to travel on in order to make the trip work.

If you list the specific trains someone could tell you which you absolutely need to buy in advance.
For example there are everyday local regional commuter trains that don't need to be bought in advance

I don't buy rail tickets in advance in France. At most, maybe 3-4 days, depending, of course, on the destination prior to my projected day of travel. I buy the ticket at the SNCF machine using the tap contact function to pay with the credit card. This includes traveling on TGV and local trains.

Only make sure the SNCF ticket machine is not defective. If the transaction doesn't go through, and you use another credit card or a 3rd credit card, all 3 ending up rejected, it is not case of something wrong with your 3 credit cards....that's impossible.

Go to another machine, your purchase will go through.