Here is information about various ways to make the reservation. If you have an AmEx card the best way is to call SNCF. 

https://community.eurail.com/train-connections-reservations-47/how-to-get-reservations-105?postid=5747#post5747

Hi @AnnaB. 

Thanks for replying. 

Are you saying DB Bahn isn’t the correct train to get from Frankfurt to Paris and that it is SNCF? 

I’m a little confused with which train company does this journey (and unfortunately no Amex card).

Thanks

I think most of the trains are booked - had to go another way.

Thanks

Its COOPeration-the very same train can be either from DB or SNCF and-by magic, without even changing the paint etc-at the border it becomes the train of the new country. This magic has been applied to EUR-s trains since nearly 100 years now. But newbees from far away do not understand.

In fact even in OZzieland down yundah they can do that with Vicrail and NSW-Sate Rail.

Now you have to grasp the basics of using th pass: going OVER the border cost an awful lot more and has fewer trains and hence is troublesome; SO-use brains; the ALternat. is to use local trains shuttle over the border-short distance and IN DE you do not need to RES but In FRance need to for the TGV-for this the hourly TGV Strasbourg -P are best, and get there -use that planner-by tiny overcrowded shuttle SWEG diesel from Offenburg.

But you can use numerous other ways to see more and explore if you have some more time and do not want the super fastest.