Hey I have the same problem as this (pm-hibernate not doing anything and not producing a log file, hibernate option greyed out in every interface), except I'm on xubuntu, not sure if that makes any difference. I followed the steps described in the chosen answer, and it still doesn't work (also, pm-is-supported --hibernate does not seem to do anything either).
Maybe I misinterpreted how I was supposed to edit /etc/default/grub. Currently the corresponding line is set to
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash UUID=da462d1a-465f-435a-acec-1689eeaca9a6"