Getting a rail reservation with a French Rail Pass

You should list all your routes here. And is your trip coming up 90 days from now?

CDG to Bayeux,
Bayeux to Reims,
Marseille to Chartres

No it is in May

CDG to Bayeux,
There are no reservations needed on this route. You need to get to train station Gare St Lazaire in Paris from the airport by whatever public transit you choose. Budget about 15 euros on commuter trains or Taxi is about 55 euros flat rate more or less at an official taxi airport stand.

Bayeux to Reims,
Then coming back you need to go from Gare St Lazaire in Paris by public transit to Gare de l'Est. in Paris where you can catch a TGV that requires a reservation.

Marseille to Chartres TGV to Paris Gare De Lyon (you need reservation then take public transportation to Gare de Montparnasse.
Gare de Montparnasse to Chartes you don't need a reservation this is a regional train.

When is the trip exactly. If it is over 90 days away there may not be a schedule to make a reservation yet.
I never use a rail pass but since you have one it will work out. It is very common problem question here

How and when do I make those reservations?

Actually you can book your reservation now I see the schedule Marseille to Paris is through May
https://www.eurail.com/en/book-reservations

I bought them from Rail Europe
The first one we would like to do is from CDG to Bayeux on the 12th of May.
Then after a few days to burn off the jet lag, would like to depart Bayeux the 15 of May to arrive in Reims to meet our R/S Eastern France tour.
Finally, we want to go from Marseille on the end of the Eastern France tour to Chartres on the 28th of to meet our R/S Southern France tour on the 29th

Does that make sense?

If you have a pass :
You just need to book a seat reservation Marseille to Paris and Paris to Reims.
The other legs CDG to Bayeux and Paris to Chartres (when coming back from Marseille) do not require a seat reservation. You sit wherever open,
Also depending on the time you want go Paris to Reims you might not need a seat reservation. You might have to take two trains that don't require seat reservations. It is only the TGV direct trains on that route that requires a seat reservation.

https://www.eurail.com/en/book-reservations

Thanks for the help. So I should be able to use the "Rail Planner" app from eurail to book the two reservations with my Rail Europe Pass?

That is what it says.
Here are the instructions
https://help.raileurope.co.uk/article/43452-how-to-book-an-eurail-seat-reservation

Bayeux is a nice town I went to the American Cemetery and the D-Day beach from there on a day trip

For your next trip to France, and I hope that there will be a next one, I suggest that you price the various train routes before buying the pass. In this case:

• Paris to Bayeux: €41 as a last-minute walk-up fare (it is not easy to know when exactly you will get to the station in Paris, so this is probably best)
• Bayeux to Reims via Paris on 15th May: €33
• Marseille to Chartres on 28th May: €43 with low-cost Ouigo, or €62 with normal TGV

That's €117-€136, vs €145+2x€10 reservations = €165 with the pass.

In this particular case, I do not think it makes sense to cancel your pass altogether, because that would only save you about €20 with the 15% cancellation fee - not worth the hassle.
But keep it in mind :-)

Balso proving one again that passes are not longer simple and they are always more money than just buying the tickets from the actual companies that run the trains.

Thank you for all your advice. When I try to book some sections on both legs I get this notice:

"No price results were found for this connection. It is possible that the train is fully booked for pass holders. Please try searching for another connection or find an alternative way to book."

What are my options then?

If you keep struggling, look into cancelling your pass (please double check cancellation policy, the 15% fee is quoted from my memory!) and booking normal tickets on SNCF Connect, Rail Europe, or Trainline (small fee for the latter two, but some folks find them more convenient). You will not lose any money, as I showed above.

And as said above, the ONLY legs you can book with a pass are Marseille-Paris and Paris-Reims. No booking needed (possible, even?) on other legs.

Did you have any success booking Marseilles to Paris or Paris to Reims?

I have already activated my pass. From what I understand I would not get a refund.

I was able to select the Bayeux to Reims but it says I need a two reservations , from Bayeux to Paris and from Paris Est to Champagne-Ardenne, Both are 10 euro but I do not see a way to purchase the reservations on the app.

You might have to change the times of day to ones you don't prefer the most unfortunately. Did you at least get Marseilles to Paris.

OK, after much head scratching I was able to get a reservation for both of us on the Paris-est to Champagne-Ardennne leg.
However, when I try to book the Marseille to Paris leg the schedule is not available yet so I will try tomorrow. Thanks for you help. I would have never been able to do it on my own!

Thanks. I was able to secure a reservation for one segment of the Bayeux to Reims that required reservations. Since the rest of the trip does not require reservations, I should be able to just book the non-registration sections on my rail pass?

I was able to book the Paris to Champagne reservation and the Marseille to Paris Reservation OK and I have paper copies of both. However, on the St Lazare to Bayeux train it says I need a reservation also, but when I try to buy one it says they are not available???

This is what the reservation program tells me when I try to book a reservation for St Lazare to Bayeux:

No price results were found for this connection. It is possible that the train is fully booked for pass holders. Please try searching for another connection or find an alternative way to book.

All trains for the 12th of May say the same thing.

Maybe it is too soon for that route? Have you checked if you can book a reservation for, say, next month?
Don't sweat over it and check again in a few weeks; the trains out of Saint Lazare don't get full.

For these TER trains in Normandy, even SNCF (the operator) themselves are giving conflicting information, depending on where you look or ask:

A
NOMAD TRAIN; Problem journey not exists
@Nanja is trying to get this cleared up.

According to this page, reservation is only needed on Friday/Saturday/Sunday and holidays on these KRONO/KRONO+ trains:

Paris <> Caen <> Cherbourg
Paris <> Trouville/Deauville
Paris <> Argentan <> Granville
So on 12 May, you don’t need a reservation. On 15 May, you would need a reservation but SNCF still say, when asked, that you can stand if no seats are available (thereby implying a reservation is not required). I'd ask at the ticket counter in Paris or Bayeux on 12 May about your journey on the 15th. These TER reservations cannot be done (yet?) via Eurail and SNCF refuse to do pass reservations via the phone.