Hi, Me and my friend who I'm going interrailing with discussed last night which trains we would take from our home town (Roosendaal, in the south of Nehterlands) to Paris and the train from Paris to Barcelona. For both routes, there was one option still avaible for us to take the day we wanted to travel. My friends booked her reservations last night, but when I tried to do it, it gave an error message a bit further in my shopping kart. So I decided to try again this morning, however now both reservations I wanted to make are completely booked full and so are all the other trains that same day. I've already booked the hostels so it is quite important to travel that day. Plus my friend already has her reservations. 

I am kind of freaking out a bit right now and do not really know what to do. Is there any possibility of making a reservation elsewhere than the interrail site? Or does anybody have any tips on how to get from one destination to the other in a different way?