Cannot boot into download or recovery mode

Hi, my samsung Tab2 is stuck at the "Firmware upgrade encountered an error" screen. No matter which combination of buttons I press, I cant get into download or recovery. I've tried flashing with Odin, it shows successful but nothing has changed. I tried the ADB command but it says "Waiting for device". When I plug in the tab to the charger (or when I connect it to the PC) it comes on automatically with the "Firmware upgrade encountered an error" screen. Is it a power button thing or is it something else ?

Thanks.
Sachin