1. Make sure pm-suspend is working on your system. You may also need to sudo first. Some services can prevent a system from going to Suspend.

2. There's also the possibility your machine is using another event name for the lid.

Close and reopen the lid whilst running in a x-terminal:

This will capture the actual string of acpi events passed from your hardware when you close the lid and reopen it. The string generated needs to be passed to the event=XXX in the lid file.