@Nanja do you have any advice, please?

You can also try:

1. Deutsche Bahn phone service (+49 30 2970, available 24/7). They can also book domestic trains in Spain.
2. Belgian railways phone service. According to their documentation, they can also book domestic trains in Spain.

Which exact trains are you trying to book and on which date(s)?

Thanks. The Spain (Madrid-Barcelona) leg I know is only available in the station or by calling and doing a hold 72 hours before departure. I’m trying to lock down the Barcelona-Paris (TGV 9702) leg of the train travel on December 3rd. And likewise, the return trip from Paris to Figueres Vilafant (TGV 9713) on December 11th. 

Will both those services also book the TGV trains too?

Both services I mentioned can also book the TGV trains between France and Spain, sorry if that wasn't clear. And send the reservations via the post.
Please note that Deutsche Bahn's number should be +49 30 2970. The number I mentioned first doesn't seem to be reachable from abroad (I just tried).

Thank you. Unfortunately, sending via post seems to be my problem since the departure dates are a week and a half away. I can go through the booking process on the eurail website, but since they require being sent by post, I can’t finish the reservation process since the website says they won’t arrive in time. So I’m looking for an alternative method other than the night before the train departs, which is when I’d be in Europe to go in person to a train station to reserve. 

The reservations for the TGV France - Spain are only available on paper and will have to be sent via the post. The only alternative to going to a ticket office is to phone Spanish railways at +34 91 232 03 20, but then you'll need to pick up the reservations at a Spanish station within 72 hours.

I'm sorry but French and Spanish railways are not exactly customer-friendly.

 No worries. This is very helpful. I was wondering if there we alternative options and you’ve helped me see that there doesn't appear to be any. Thank you. 

Hi @Emily, I see rvdborgt gave the right answer already. Unfortunately, the reservations are only available in paper, so you'll have to try making the reservation when you are at the train station. Cheers, 

@Nanja 

Frankly, I find it incomprehensible that it is not possible to deliver tickets by post 1 week before departure date.

May I ask where the tickets are sent from?

If you want to book a train from Paris to Barcelona. And you want to have this delivered in Belgium, the Netherlands, France, Germany, .... , then this should be possible within a week, right?

@Sven 

I am not 100% sure but i imagine that someone mentioned Ireland (but i guess that was where the paper passes came fom).

Nanja enjoy a long weekend Therefor she asked to tag @Leo  or @Felipe.iturrieta  for urgent cases

Hi Sven, it takes a while to confirm, process, print and ship, and since we don't work weekends, it would have to be done in 5 business days. Not only that, but reservations for France-Spain are often unavailable a week before the travel date. So this time requirement is there to avoid the high risk of customer paying for reservations and not getting them in time. In cases where you travel within a week and only paper is available,it's best to book at the stations. If you have any further questions on this topic, you can tag Felipe Cheers,