Pantheon ticket system

Wish I had a definitive answer for you but having just spent some time (again!) on the website (https://www.pantheonroma.com/home-eng/) plus done some digging around for very recent reviews/reports, it appears that they're working out some glitches.

Here is a TA report from someone who was just there yesterday:
https://www.tripadvisor.com/ShowTopic-g187791-i22-k14451427-New_ticket_system_at_the_Pantheon_not_a_good_experience-Rome_Lazio.html

And an article in "Wanted in Rome":
https://www.wantedinrome.com/news/italy-rome-pantheon-makes-20000-on-first-day-of-ticket-sales.html

There does not appear to be a place to order advance, regular-entry tickets on the Pantheonroma site; you have to go to the one live-linked in this article:

https://www.wantedinrome.com/news/how-to-visit-the-pantheon-in-rome.html

"The tickets - available at €5 (full price) or €3 (discount) - can be purchased online via the Musei Italiani website www.museiitaliani.it (registration required)."

But you can also purchase them onsite:
"Tickets can also be bought directly from the official ticket office at the Pantheon, with payment by credit card or debit card, from 09.00 to 18.00."

Honestly, if your trip isn't until the 18th, I'd sit on it a little while longer and see if they get some bugs ironed out. I'm frankly puzzled that they're not selling advance tickets on the www.pantheonroma.com website or even instructing people how they're supposed to get them. If you end up just planning to get them at the Pantheon, I'd advise getting there at the opening hour.

Thanks much for your effort Kathy! I saw the TA reviews also. Not going so well. :( From just those experiences we decided on the “wait and see” method. Agree with your thinking.

Will cross fingers that it works out for you one way or another!

Looks to me like they jumped the gun on the whole business, eh? It may have been better to introduce/test the ticketing system in low season versus smack in the middle of the high one.

My words and thoughts exactly Kathy!