First rule of asking a question like this: try to be as precise as possible. What date you’re taking the trains? Which trains you’re taking specifically (departure time, train number,...) ? Otherwise it’s very difficult to help or suggest proper alternatives here on the community.

Seems a bit tight transfer times, especially for the leg to Barcelona.

Oct 4 date of travel.

 08:25am. Nice to marseille st Charles.

11:24am. Marseille st Charles to Nimes.

 12:46am. Nimes to Barcelona.

Oops 12:46pm

Thanks for all advice!

First train number# TER17478

Second train number# IC4760

Third train# TGV9713

On a train keep losing internet connection. 

Other route planners suggest a change in Narbonne with a bit more time:

So you might want to change trains in Narbonne, to have a bit of extra buffer.

For my personal standards, it’s a bit too tight for the very infrequent connection to Barcelona. But coming from Nice, you don’t have a lot of other options.

If it goes wrong, speak to staff to get you rebooked to the later TGV. Worst case is that you have to wait a long time in Narbonne, or Nîmes. But both are well worth a visit for a couple of hours.

I don’t show the 4760 train stopping in Narbonne?

Because the rail planner app probably makes you switch in Nîmes, not Narbonne. Narbonne is some stops further.

Thx. Can I book through another App?

Rail Planned?

Rail Planner.

You cannot book seat reservations through the app, it redirects you elsewhere. The Rail Planner app is useful to log each train you'd like to take -> QR-code = your ticket. Have a look at this page : https://www.seat61.com/how-to-use-a-eurail-pass.htm#how-does-a-eurail-pass-work

To book seats you have to use eurail.com (2€ fee per person per train) or other websites : 

Just add each leg separately : Marseille - Narbonne and then Narbonne - Barcelona.

For French domestic trains you can also use this link (4€ fee per order) : https://travel.b-europe.com/Eurail-GE/en/booking-tgv#TravelWish

What is your travel date ? Btw what do you mean by I have booked my train trips ? Have you paid for reservations already ?

Yes I have paid for reservations. Thx for helping.

Just to clarify I booked my train tickets with a global Eurail pass and then made reservations on Eurail website because the Eurail app doesn’t allow it. Thx for the advice.

Another naive question? If I leave my tight train transfer schedule as is and a train is late and I can’t make my transfer can I use that missed  train reservation on the very next train? 
 

thx

Obviously not the same seats but at least get on the train.

In case of delays, you’ll have to speak to train staff to give you a proof of delay, and then to station staff to get you rebooked on the next available train.

Interrail should be considered as a through ticket, so they should rebook you without trouble.

I agree with Brendan, just follow your original plan and if anything goes wrong speak to staff. I wouldn't buy new reservations.

It is also possible that the TGV coming from Paris is delayed and you have a longer stop in Nîmes... :)

Thanks for all the great advice!  
Cheers, Brian