I just bought a train ticket to Salerno at Termini Roma. I had to use the ticket office because the ticket machine asked for my code (probably a Green Pass code) and as an American I didn't have one. I asked the ticket agent and he said I would have to use the ticket windows and not the machines as I didn't have a code.
What about small stations that don't have agents? Maybe those are served only by regional trains, which I think do not require a Green Pass?
Has anyone else had experience using their vaccination documents at the ticket machines? It is inconvenient to go to the ticket window.