I can suspend manually but not automatically - such as changing the power settings to suspend after an hour of inactivity.

Here are the contents of my /etc/default/grub

GRUB_DEFAULT="0"
#GRUB_HIDDEN_TIMEOUT="0"
GRUB_HIDDEN_TIMEOUT_QUIET="true"
GRUB_TIMEOUT="10"
GRUB_DISTRIBUTOR="`lsb_release -i -s 2> /dev/null || echo Debian`"
#GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
#GRUB_CMDLINE_LINUX_DEFAULT="quiet splash pcie_aspm=force resume=/dev/sda5"
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash pcie_aspm=force"
GRUB_CMDLINE_LINUX=""

Any suggestions out there? I would be grateful for a fix.