Hello,
Per the Italy guidebook, looking to buy advance tickets on Ticketone.it - I will be there on April 2, 2025. At the site it appears that you can only buy the express (day) tickets for the current month. In this case only up to January 31. There is a calendar - but you can't advance it to the next month. Site glitch or am I missing something?
Assuming that is the official site you are probably just too early for April tix
As well, I don't see any need to purchase in advance. It's a huge site that can handle a LOT of people. I know that they're initiating daily visitor caps (15,000 in the morning and 5.000 in the afternoon) from April 1 - October 31 but I still don't think you need to be concerned at the time of year you're going.
“Assuming that is the official site you are probably just too early for April tix”
Yes, that’s the official online seller for tickets to Pompeii and Herculaneum. I’d agree that it’s too early to buy tickets for April. OP, try buying them in mid February as they should be available then. Good luck and happy travels!