MacBook Pro won't go to sleep when lid is closed

I have a Late 2011 MacBook Pro and I just got it back from the repair shop (mainboard was swapped). I immediately installed OS X El Capitan (before it was Yosemite) and found that when I closed the lid, the Mac would not go to sleep anymore. Even testing in other user's accounts and after restarting, resetting NVRAM and SMC and even booting from a different hard disk (with OS X Lion installed), it won't go to sleep and also the little LED on the right will not light up, neither while booting nor when I close the lid. Running pmset -g assertions in Terminal gave this output: Assertion status system-wide: BackgroundTask 1 ApplePushServiceTask 0 UserIsActive 1 PreventUserIdleDisplaySleep 0 PreventSystemSleep 1 ExternalMedia 0 PreventUserIdleSystemSleep 0 NetworkClientActive 0 Listed by owning process: pid 54(configd): [0x00000054000701d1] 00:02:13 DenySystemSleep named: "InternetSharingPreferencePlugin" pid 102(hidd): [0x0000001e000901ba] 00:03:07 UserIsActive named: "com.apple.iohideventsystem.queue.tickle" Timeout will fire in 894 secs Action=TimeoutActionRelease pid 44(UserEventAgent): [0x00000030000b01cd] 00:02:48 BackgroundTask named: "com.apple.mds.0" Created for PID: 64. pid 44(UserEventAgent): [0x00000006000b0137] 00:03:30 BackgroundTask named: "com.apple.metadata.mds.power" Created for PID: 64. Kernel Assertions: 0x100=MAGICWAKE id=501 level=255 0x100=MAGICWAKE mod=01.01.70, 07:30 description=en0 owner=en0 Idle sleep preventers: IODisplayWrangler I have prevented bluetooth devices from waking the Mac, but otherwise I am not sure what to do. Could it be a hardware issue caused by the replacement of the motherboard?