It might help if you say which trains you're talking about. From where to where?
The Euskotren network isn't covered by Interrail, for example. But I don't think that shows in Rail Planner
All Renfe trains except Avlo are included, but most trains do require a reservation. If staff told you otherwise they were not well informed. You should be able to book reservations through raileurope.com for those requiring reservations.
But raileurope (and happyrail) still have problems with several trains from northern Spain to Madrid. Raileurope shows normal fares for each train between San Sebastian or Ourense and Madrid right now.
If you want information on a certain train, then please always mention route, date and departure time.
We can now book the most trains. So maybe the staff was not so good informed.
but I have problems with rail Europe because in the app I can’t add my interrailpass.
We booked The last few trains via renfe directly at the trainstation. This worked best for us.
How do you manage the reservations?
We can now book the most trains. So maybe the staff was not so good informed.
but I have problems with rail Europe because in the app I can’t add my interrailpass.
If you use the Rail Europe app, then be aware that the iOS app doesn't have "Add rail pass” yet. The Rail Europe website does have that option, including the mobile website.