Even if you upgraded to the 3D-enabled firmware 3.50 and connected your PS3 to a 3D display, the PS3 may not be able to playback in 3D mode.
Games will tell you that it can’t operate in 3D and while playing 3D blu-ray discs you’ll get the following error message “This blu ray disc requires 3D player connected to a 3D display.”
The fix is as simple as changing a setting.
1. While in the PS3′s XMB/menu go to Settings>Display Settings>Video Output Settings
2. Run through the Automatic Detection Process and it should detect your 3D display
3. Enjoy your games and movies in 3D!