On which route couldn’t you find seat reservations ? We’ll gladly help you here if you give us the route, date and ideally departure time. Have a look at this link too : https://www.seat61.com/interrail-and-eurail-reservations.htm

Trains in Spain can only be booked at RENFE ticket counters. It’s not that they’re full but more that RENFE doesn’t want to sell them online… hopefully it’s not this that made you cancel. The website is not clear about that (and on a few other points too).

Otherwise for most trains (except Eurostar, Thalys, TGVs to Belgium) there’s no quota for passholders. As long as you can buy a regular ticket, you can obtain a seat reservation. And still there are always alternatives, albeit sometimes a bit slower.

Which route did you book ? Not possible as you only paid the passholder seat reservation and not the ticket. However on trains with optional reservations yes you should be able to buy a ticket + use the seat reservation.

Thanks for the answer. I was looking for trains from St jean de Luz to paris, from london to amsterdam, even i fthey let me mke the reservation, when i was doing the final payment an error pop up every time….

i book paris london with  eurostar

You can't use the reservation without an Interrail pass. 

No indeed you can't and tickets are very expensive…

Interrail has often bugs during the booking process. It may not mean that the trains are sold out.

If you haven't cancelled the pass yet, let us know your travel dates and we'll gladly give you advice.

There are multiple TGVs between St-Jean-de-Luz or Bordeaux and Paris. It's strange that you didn't find one available.

London - Amsterdam Eurostars are not frequent at all (and very popular). However you can change in Brussels and there are more trains and seats available !

Again let us know and I'm sure that you'll be able to travel with your pass (while saving money !).