It takes about 30 seconds for the TV to warm up, so normal brightness may not appear immediately.
The TV has a fan to keep the inside lamp from overheating. You'll occasionally hear it working.
PROTECT STATUS
Attempting to turn the LED on fails repeatedly
If turning the lamp on fails, the set automatically tries turning the LED on 3 times. If all attempts fail, all LED's on the front panel will blink. Check the LED,LED Driver and Sub power check the LED,LED Driver and Sub SMPS and replace them if necessary.