Yes contact customer support here : https://eurail.zendesk.com/hc/en-001/requests/new If you mention your travel date in the header, they will answer faster

Btw there are almost always other better websites (less or without booking fee) to check availability and book seat reservations, see :

https://community.eurail.com/train-connections-reservations-47/how-to-get-reservations-105

https://www.seat61.com/interrail-and-eurail-reservations.htm

https://www.b-europe.com/EN/Booking/Pass#TravelWish (Thalys and Eurostar)

https://travel.b-europe.com/Eurail-GE/en/booking-tgv#TravelWish (TGV in France)

Let us know the route, date and departure time and we'll be able to help you with alternatives

Looks like I’ve stuffed up worse than I thought. I checked https://www.b-europe.com/EN/Booking/Pass there aren’t any tickets available on the Eurostar on the 29th May. Silly me thought that if there were available on the Eurostar site I could book those seats with the pass.

29 May is Whitsun Monday. Lots of people travelling. And Eurostar have limited pass holder seats.

Yes Eurostar sells out weeks in advance…

There is a seat on 29th May to Brussels 08:16 - 11:12. Book it ASAP (there are at least 4 seats)

Otherwise 28th May London - Lille 19:34 - 22:00 30€

Or ferries but it'll take a long time…

What is your route ?

Thanks to all for the feedback and tips.

I’ve decided I’m going to refund the eurail pass and book direct through the train companies. I realise now I should have booked all of the trains before accomodation so I wouldn’t be tied to a stringent schedule.

Travelling with 2 young children means I’d rather pay extra and be able to choose more convenient travel times.

The additional cost is very disappointing but it’s a lesson learned.

Well what is your route ? In most of Europe you can board any train you want, with the pass. There's lots of flexibility ! Otherwise advance tickets are tied to a specific connection...

France and Spain are the worst countries as they require seat reservations for a lot of trains. But it is entirely doable booking seat reservations 1-2 weeks in advance and it'll be cheaper than regular tickets

Germany, Austria, Belgium, Netherlands, Switzerland and the UK are fantastic with the pass as you can board any train with no reservations whatsoever. While regular tickets are very expensive.

Make your calculations again I'd say. If you let us know your itinerary we'll help you

Eurostar is the bottleneck and afterwards you can enjoy all of Europe very easily with the pass.

If you're going to Amsterdam, you could also take an overnight ferry from Harwich to Rotterdam. It is very convenient (direct train from London) and comfy. You also get a 30% discount for the boat. There are also more Eurostars going to Brussels and then Amsterdam is easy to reach by direct IC train (reservation-free).

If you're going to Paris check availability via Lille, there are often more seats (not on 29th May though).

Most trains to Paris are already sold out on 29th May so buying regular tickets won't help

From Paris or Brussels to London there are loads of seats

Thank you for all of the suggestions. I have booked Eurostar on 29th directly. Unfortunately our accomodation is all locked in and our transit date wasn’t flexible.

Paris to Amsterdam on June 5th was also quite booked out so I’ve had to book that direct too.

The lesson here is to book transits before accomodation in future and book the transits well in advance :(

Are you sure that you've looked correctly on b-europe ? There are loads of seats on all trains on 5th June between Paris and Amsterdam

Thalys and Eurostar are the worst trains of Europe for Eurail/Interrail users with the quotas. For all other train journeys in Europe definitely book accomodation before seat reservations (where required) as you can 95% of the time board any train you want at any time

I agree that the fact that all trains were sold out on 29th May was unfortunate but that's because it is a holiday weekend...