I'm trying to make a seat reservation for the TGV 9812 from PARIS AEROPORT CDG2 TGV ROISSY to Montpellier Saint-Roch at 09:58-14:05 on July 7. The Eurail website says that prices are unavailable for this train.
If I try to book through travel.b-europe.com instead, there are still some available seats. However, in order to book my seat, the website requests a Pass Cover number in the "Ticket Details" section. Since I have a mobile Eurail pass, I do not have a Pass Cover number and am unable to complete the reservation.
How can I receive a Pass Cover Number? Is there an alternative way to book a seat on this train? Thank you.