I have a 2 tap dorm fridge style kegerator.
My normal procedure to carbonate is to cold crash in the fermentor to 33 F, transfer to a keg, purge 02 and put c02 on it at 10-12 psi depending on what I'm shooting for. Typically in 5-7 days I'm where I want to be.
8 days ago I racked a brown porter to a keg. I had not cold crashed this beer. Put the keg in the kegerator without hooking it up to the gas to allow it to chill for 24 hrs. Hooked up the gas the following evening and let it sit for 4 days. Checked it. Nothing. Figured it must have been a temp issue and turned the gas up to 15. 2 days, no difference. took it to 20 psi, rocked the keg for 5 minutes. 2 days, no difference. Put another keg in at the same 20 psi (exact same procedure, racked warm, no gas for 24 hrs to chill) and that one is fully carbed in 3 days, porter still the same. Leak tested the keg with soapy water, no visable leaks. Pull the PRV, there's plenty of pressure in the keg.