Trains within Spain can't unfortunately be booked online. See advice here : 

The first TGV of the day from Paris arrives in Barcelona at 16:34. There are still 8 trains until the end of the day. There will certainly be seats available.

You'll be able to book seats for all your journeys at the first Spanish train station you visit.

Unfortunately Spain is quite a pain for Eurail passengers but still entirely doable !

If you are doing a certain number of legs, you could contact a travel agency, see this page : https://www.seat61.com/interrail-and-eurail-reservations.htm#Spain (very useful website btw)

Edit : the TGV Paris - Barcelona can be done on eurail.com (2€ booking fee)

Hi Thibcabe, thank you for your prompt response. So I have to be in Madrid from Jun30-Jul 03 and in Seville from Jul07-Jul10. I was hoping to visit Paris in between days (Jul03-Jul07), however, based on your message and the information contained in the link you kindly provided, there are no highspeed trains going from Madrid to Paris, therefore I should consider visiting something else during Jul03-07, and perhaps visiting Paris the week after Seville. Something like going from Seville to Barcelona staying there a couple of days, and then going to Paris. Would that make a better sense?

Yes your last plan looks nice. Madrid - Paris (via Barcelona) takes at least 10h so not worth it for 4 days at all.

- Madrid - Sevilla (Granada and Cordoba too if you've got enough time to fit those in)

- Sevilla - Barcelona 2 daily direct trains (otherwise via Madrid)

- Barcelona - Paris 2-3 daily TGVs (35€ seat reservation)

From Barcelona another option would be to take the coastal route to Perpignan (change in Portbou) and from there a domestic TGV (limited 10€ or 20€ otherwise) to Paris. It takes longer but it is certainly doable in a day while being quite scenic and saving you money :)

You could always stop for a night in Montpellier, Nîmes or Avignon (or even Lyon) along the way

Thank you Thibcabe, I’ve booked a place in airb&b for Paris for the second week of July, hopefully the July 14 celebrations will be worthwhilde rather than dangerous ;)

Thanks for the advice of the other more scenic route, definitely to be considered.

I believe I have to activate the euralpass before I do any reservations. Would you recommend doing so (both activation and reservation of trains Barcelona-Paris) since now?

You do not have to activate the pass to make reservations. Once you add a valid unactivated pass to the eurail website you can use it to book reservations.

The other sources listed above do not require a pass to be held at the time of booking, only when travelling.

You should book the Barcelona - Paris route well in advance as it only has 2-3 trains daily and is very popular.

I second that you need to book Barcelona - Paris ASAP. 35€ +2€ booking fee on eurail.com or you call SNCF (no fee).

Some dates in July are already sold out. There is always the option to go via Portbou but I'd also book the TGV in advance

Thank you for all your comments and suggestions, unfirtunately, I feel lost and frustrated. I’m in the eurail.com website and can’t find my way to book reservations for Barcelona to Paris ;(

Ok, it seems that I finally got it. At least the first leg from Barcelona to Paris. I’ll figure out the following trips to get down to Reggio Emilia…

Thank you both!

Go to Seat reservations, fill in the search form and click on the Search button:

You must be logged in to book, but the page should offer to log in.

Where do you get stuck?

Thank you RVDBORGT! The screen was not showing any options but after several screen refreshes it showed up and booked appropriately ;)

Any suggestions going from Paris to Reggio Emilia? In some cases I’m getting a “PASS NOT VALID” message...

That screen is showing the correct information, the direct Paris - Milan Frecciarossa trains are not valid with passes, only the Paris - Milan TGV are.