Get the shutdown error code-
Make sure lamp, lamp door, back cover, etc is installed properly.
Plug in Tv.
After Tv initializes press power to turn it on.
The Tv should try to turn on a few times then shutdown with the red light.
Go up to the front panel on the Tv, press and hold MENU + DEVICE (INPUT) until a light on the front starts blinking a two digit code like 3 blinks pause 4 blinks repeat, or 5 blinks pause 6 blinks repeat, etc.
Report back here with the error code.
Other thing you can do is pull out the old lamp and look at it. If you see dirty dingy inside, cracks on the reflector, shattered pieces inside, bulging area at the bottom of the stem, then the lamp is worn out.