Trainline warning

Trainline is a third party vendor. It's always best to book directly with the train company, using the appropriate app. I doubt if a September train schedule and tickets have been released by the company yet.
Wishing you a great trip!

I just did a dummy booking on Trainline for those trains, and I did not get that warning. I would exit out the website and try again.

Have you tried the Trenitalia website?

I see that one, but in also see one that leaves at 7:30 but arrives Naples (five hours 40 minutes).

But I’m not getting that message about “Careful ! . .” — so I am not sure why you are getting that.

There's absolutely no problem buying from Trainline, and it fact it makes sense where you have choices between train companies — as in Italy when you have the possibility of combining Trenitalia trains with Italo trains, or on some routes in France, where you can choose between SNCF and Trenitalia.

Yes I did exit the website and tried again with the same result. I'll give it try another time.
Should the September schedules be out by the week of June 9?

Thanks everyone. I'll try both sites again another day since frustration is settling in.

I was told on a previous post that the train companies should be releasing their September schedules by June 11/12. Is that about right?

Schedules for Regional trains are probably not yet released. If you want to check your options test a date this coming week. Scheduled trains don’t change much.
Use the www.trenitalia.com website.