It looks like you have a filter set. Maybe direct trains? Because there aren't any direct trains from Paris to St Louis. You need to change in Strasbourg or Mulhouse. The first departure after 14:00 is with a change in Mulhouse.

If you're still 4 persons, then the cheapest is to book this via b-Europe:

https://travel.b-europe.com/Eurail-GE/en/booking-tgv#TravelWish

There still availability for €10 (+€4 booking fee per order).

Hi

Thanks for Yr infor, I try other reservations also same problem,  it mean I only can book the train if it is direct train?rvdborgt. Tq

British trains cannot be booked via Eurail.

They can be booked free of charge via LNER (LNER trains only, such as Newcastle to London) or GWR (all train in Great Britain that have optional reservations). Day trains in GB only have optional reservations. The Eurail website and app are wrong about this.

By the way, the destination you have selected here is not in London, it is the station "London Road” in Brighton, at the English south coast.