We were just discussing in another thread whether you could get back into Chromie Time at level 48 or 49, this appears to confirm the suspicions that you cannot.
The one thing you could try is abandoning “A Chilling Effect” and then trying to turn Chromie Time back on before the quest is re-offered. Udiza wasn’t able to get that to work on a trial character, but she wasn’t sure if that was affected by it being a trial character.