Regional train schedule changes on booked tickets

You can use any regional train on that route that day.

Just verify your schedule the day before, never hurts to be a bit earlier than pushing it. Italian trains are usually on time, but stuff happens.

Regional trains have no seat reservations so you can get on any Regional train headed in the correct direction and within the valid time period for your Regional train ticket -- general four or five hours. If the Regional ticket came as part of a ticket package it should indicate a valid time period for that ticket.

The regional portion has a specific train number and time but this has changed since I booked, so I guess I can just take the most convenient to make the connection

Regionale trains e-tickets are train specific, but they can be changed for free unlimited times before the scheduled departure time of the chosen regionale train.

Do as suggested in this thread and you'll be fined.
Did you get your tickets on trenitalia.com on on a reseller's site?

Do I then have to go to the ticket window to change the regioinale train?

When you say that the numbers have changed, what do you actually mean by that? If these are paper tickets the numbers can't change. And you say that in the app the numbers have not changed either.

Maybe tell us what you booked?

You do not need to go to the ticket window. You cannot change electronic tickets there anyway. Tickets normally get automatically validated for the train you selected during booking. If you miss a connection due to a delay you can however just take the next one.

Thanks but I am not clear about this. They changed the regional train numbers and times (slightly) since I booked. Do I just take the closest, most convenient regional train? And if I understand you, there is no more validating machine for electronic tickets?

Do I then have to go to the ticket window to change the regioinale train?

I doubt you have to do anything because I doubt anything has changed. Anyway why would you try to change at a window an e-ticket you purchased on trenitalia.com? Log in to the site/app and change it online.

there is no more validating machine for electronic tickets?

There has never been a validating machine for electronic tickets. During the 10 months in 2023 when e-tickets had to be manually validated, you had to push a button on your screen.

They changed the regional train numbers and times (slightly) since I booked.

Again, who is "they"? Where did you book? What Regionales are you taking and when?

When I go to the TrenItalia website and look for regional trains where I have to make a connection, two trains I was ticketed on (e-tickets) no longer have the same train number. There is no change in my app, however. I assume that with the schedule changes there were adjustments, so the 'they' refers to TrenItalia. If no reservations are required on regional trains, can't I just get on any closest to my reserved train?
These are the first e-tickets I have ever bought. On my last trip years ago there were no e-tickets and I remember being fined for not validating my regional ticket in the machine.

It is also very well possible that you are not interpreting what you are seeing correctly...

But I can only guess.

These are the rules (from The Man in Seat 61)-

In August 2023, Trenitalia made a simple thing unnecessarily > complicated. For tickets bought online, the old system of having to stamp your ticket in a validator is gone, as is the system of tickets only being good for a 4-hour time slot. Regional tickets bought online are now only good for the specific train you select, but you can change this free of charge as follows: Until 23:59 on the day before departure, you can change the date and/or departure time free of charge using the Trenitalia app or website, as many times as you like. Tickets are 80% refundable. From 00:00 on the day of travel, tickets become non-refundable, but you can change the departure time as many times as you like free of charge until 23:59 or the last train, whichever is sooner. However, at the departure time of whatever train is currently selected, the ticket is considered 'used' and no further changes can be made. Obviously, this means that if you decide to take a later train you must change your departure time in the app before your original train leaves! Online regional tickets bought from a retailer such as www.thetrainline.com or www.italiarail.com also work in this way, you'll get a link to make changes to the date & time. You show the QR code on your phone or can print the confirmation email with the codes on.

ALSO-

You can buy regional tickets at the station on the day from a Trenitalia ticket machine or ticket office. The ticket may be for a
specific departure. You must validate it by sticking the end of the ticket, blank side up, into one of the green validator machines at the entrance to (or on) the platform. Convalidare sul retro on the front means Validate other side!

​How complicated! I'd be afraid of making any change on the app for fear of messing up the reservation. I shall go to the ticket window to enquire.