MacBook does not go into sleep mode

My MBP does not go into sleep mode even though I have configured system preferences to sleep if the system is idle for 10 mins. Instead, the systems sleeps only when battery power is completely drained. This is really frustrating!!!

Is this a known issue, or are there additional troubleshooting steps I need to perform.

thanks!

I know there's a battery update available on the Apple support but I'm not sure if this will solve your problem... worth a try anyway.