Brig - Venezia Mestre

02.08 - 09:44  Reservation via tickets.oebb.at - select ONE WAY TICKET and then at adult the discount Interrail/Eurail Global Pass. 11€ in 2nd class You can buy the reservation also at ÖBB Ticket Offices.

Udine(It) - Villach (Aut)

05.08; 15.16  This Railjet train has only optional Reservation, but for the Italian part you have to pay 10€ fee. This fee you can buy via tickets.oebb.at - select ONE WAY TICKET and than at adult the discount Interrail/Eurail Global Pass. 10€ in 2nd class. Reservations are 3€ extra with seat only option. If you buy this fee at Italian Stations you get a Reservation for free on top. You can buy the fee also at ÖBB Ticket Offices.

For the French trains online only possible via Interrail.eu (but only a few seats for 10€) or with an paper pass cover number (request via customer service if you have a mobile pass, they need very long) via B-Europe (few seats at 10€ and all others 20€). You can also call SNCF Call center and press #85 for English or SNCB/NMBS Call center or in France at counters. 

Spanish trains only possible at counters of Deutsche Bahn or SBB in Switzerland or in Spain at ticket offices of RENFE or calling RENFE call center and to pick up the ticket in Spain.

The Train Barcelona-Lyon only possible on ticket paper (except via calling SNCF), possible also via Interrail.eu but you will get it via postal mail. Or at ticket offices of Deutsche Bahn or SBB. 

 Here is the number for calling SNCF for the French reservations. No need of Pass Cover Number. 

https://www.sncf.com/en/customer-service/contact-us/telephone

 Press #85 for English, no booking fees, reservations are sent via e-mail.

This is no (railjet) train, and you should reserve it in advance (reservation is included with the 10 € supplement, no extra cost of 3 € for this, even if booked online with ÖBB).

The 15:16 departure is a bus. ÖBB won't let me make a reservation online, so that has to be done at a ticket office (it's optional but recommended). I doubt if the 10€ fee applies. ÖBB doesn't offer it online.

If this is the only journey on that day, then consider buying a normal ticket instead of using a travel day. Currently that journey is available for €9.90.

For an overview of how to make reservations for Spanish domestic trains, see this post.

For an overview of how to make reservations for TGV/AVE France-Spain, see this post.

You could also try if ÖBB can book any of the trains (either at the ticket office or by phone: 05 1717); if you try, please let us know what they were able to book.

Don’t know what you’re doing wrong, but the reservation for passholders is possible without any problems online.

Also the supplement / fee (that applies) and the reservation without any additional cost. It’s also possible to choose the exact seat you want. Reservation is optional, that's correct, but it's free and you avoid the risk of not getting on.

Right, I see it now. The website proposed the €9.90 fare because that's cheaper than the infamous 10€ supplement...