not sleeping on lid close

Ever since I replaced the thermal paste on the system board (see "reflow" procedure - very involved and requires completely removing system board from laptop - all cables removed, etc.) my laptop hasn't been sleeping on lid close.

It will sleep if I select it from the menu, or eventually as part of the Power Saver prefs, however.

Is it possible I left a cable loose and if so, which one is it?

Could this be fixed by a pram reset?

Anything else to look at?

It's been running great with new thermal paste, no longer panicking on video issues.

Thanks!