If you bought your VFT this year it's possible it may be resisting dormancy because it is a young plant not too long out of TC that has never gone dormant before and doesn't really need to go dormant this Winter. if this is the case it may still very well slump into a light dormancy anyways if it is grown in a windowsill without any artificial lighting supplementing it.When should I fridge it? I'm going to have to fridge it overwinter as no part of my apartment gets cold enough, and being in Michigan, the porch gets too cold. I thought I had to wait for it to go all brown and die back before I fridged it, but that hasn't happened yet, and it seems like it should have started at least.
To make a VFT go dormant in places in the US where it gets too cold to leave them outside all year all you should need to do is place it about 2 inches from the glass of the window. The night chill on your window should make a nice little microclimate that gets cold enough to make it go into at least a light dormancy every Winter and that is all a VFT really needs. VFTs don't really need temperatures much below 50 F to go dormant, especially red forms. Refrigerator dormancies or garage dormancies are overkill. The VFTs can still photosynthesize all Winterlong in a windowsill but not in a refrigerator or garage.
There are VFT growers in CA who grow VFTs in greenhouses and their night time temperatures sometimes don't even drop below 50 F during the Winter. They often have daytime temperatures that soar into the 80s F in their greenhouses and yet their VFTs still go dormant every Winter just like they are supposed to.