Going to sleep issues

so lately having trouble 2011 mbp going sleep (now talk baby )
when close lid, not go sleep node. resetted pram (or whatever when have hold down command option p , r when booting, didn't help. tried is, checked if go sleep when runs on battery, , tadaaaa: does! (btw: indicator in pulsing light in front. meaning: when close lid , on battery: pulsing = sleep mode. when on ac , close lid: not pulsing = not in sleep mode.)
has ideas why id doesn't go sleep mode when running cable?

 

mac os x: why mac might not sleep or stay in sleep mode
determine why mac wakes sleep

 

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