I know this topic has come up several times on this forum, but I wanted to add another data point (and vent my disappointment haha).
I had scheduled a night visit to the Colosseum with Walks of Italy back in July for my visit to Rome this October. The night visit includes the arena floor and underground. I knew about the troubles of tour companies cancelling on people who had bought tours that included the underground, but I held out hope that this one might be different.
Well, just this morning I received an email from Walks stating that "due to a technical issue" (their words) they "were unable to confirm the tickets" (again their words) for me. They automatically moved me to a day tour of the Colosseum with the Forum and Palatine Hill for the day before.
I thought this was kind of messed up since it's on a totally different day and I'm not even going to be in Rome that morning. It doesn't bother me personally since I had already booked the daytime tour on the same day as the night tour (I wanted to see it both and day and night and also figured this would be good insurance in case the night tour with the underground was cancelled), but still I'm thinking of other travelers who may not have that flexibility.
Anyway, just wanted to put that out there in case anyone else is in a similar situation.
If I still wanted to see the Colosseum at night, do I have any other hope at this point?