My L1919S screen has been working fine for two years. Now, without any warning, it seems to have no power. Everything is plugged in and power is available but it will not turn on, either automatically as usual, or by the on/off switch.

The computer power switch may be faulty - they often have a fragile plastic link which fails.
People say they are built to fail just when they are out of Warranty.
It may well be a power pack failure in the comp - they are not too expensive but need to be fitted by a pro.
If you are in the UK you can still return to the seller or maker and say 'This computer failed after only 13 months (or whatever) and so is NOT FIT FOR PURPOSE'
Come back here if you need more guidance

If the laptop battery is more than 3 - 4 years old then the battery could be worn out. Rechargeable batteries have a finite number of charge and discharge cycles and will lose their charge capacity over time, i.e. won't charge to 100% and gradually the charge reduces until the battery won't charge up at all. OR The battery shows a 100% charge but when the adapter is disconnected the battery drops off to zero capacity in a very short time. If the battery drops to an unacceptable charge level then the battery needs to be replaced. Rechargeable batteries will fail if stored in a discharged state for long periods.

Suggest you pull the plug out, remove outer cover and place a cup of water into the micro. Set power to minimum then switch on and take note if the fan works or not. If not, switch off immediately and have it replaced(magnatron will burn out if left to run without fan.)

impeller?

You may want to borrow an a/c power source for you laptop... just to check to see if yours is non functional.
If the a/c isn't charging the batt, then no matter what config, it won't charge... seems like this may be your problem
The icon may be sensing a connection even if there's no power...not sure... make sure the connector isn't distorted...

LG is well known for their power supply problems.
1st things to check of course -
1) A/C power outlet it's plugged into fine or operating fine?
2) Power connection to the monitor all the way plugged into the monitor?
May be a time to find a good trust worthy TV repair shop.
Blessings,
A/V Media Guy

Have you tried the Monitor on another computer? It may not be the monitor at all and could be the video card on your computer.

you can check your lg panel on connecting it to some other cpu

Hi . I would begin by pulling the stove out and making sure it is plugged in. If it is, unplug it and plug something else into the plug like a blow dryer to make sure you have power to that outlet. If there is no power, you have either blown a fuse or kicked a circuit breaker. Go to your electrical panel to replace the fuse or reset the circuit breaker. good luck.

there is someting loose inside the computer so you may have to open it and check for loose conections or pices that they may be loose or video conectors