Help! I need a paper Passholder Number to make seat reservations but only have a Mobile Pass.

Hi all, hoping this helpful community can help me again.

I’m trying to book a seat reservation with ItaliaRail but it’s requiring a paper Passholder number and won’t (obviously) accept my mobile pass number.

Is there anyway to get a Passholder number that will work?

Thanks!

Edit to add: I’m just seeing that all of TrenItalia’s booking is down for maintenance right now, and it’s possible the reason all reservations on Eurail’s site just disappeared, is because of this, in which case, I can use Eurail—but would prefer to not be in a bind, so if anyone knows if it’s possible to get a Paper Passholder Number, I’d appreciate it!