I noticed that some Eurocity between Italy and Switzerland are not visible in the Interrail planner app (for instance, EC 50 and EC 54 MIlano-Basel). The other three connections of the day are visible. One can still reserve the seats (e.g. from the Interrail reservation system, but the interrail ticket cannot be activated) . Interestingly, if one looks at the national legs of those trains (Milano-Domodossola and Brig-Basel) they become visible, but the international ones are not.
Have others had similar experiences? Can one just add the trip manually, or will the controller object, because those trains are not supposed to be used by Interrailers (even if the seats are reserved) ?
It seems that Zurich trains are all visible, but Geneva and Basel ones are limited.