What's up with my ThinkPad T480s? Somebody help me pls

My Lenovo ThinkPad T480s won’t turn on at all. It doesn’t respond to the charger and none of the indicators light up. It hasn’t been dropped or taken for repair.

It was working normally. I stepped out for lunch, left it on (the screen turned off due to inactivity), and when I came back I closed the lid. Two hours later it was completely dead, even though it had been plugged in the whole time.

There were no prior issues — the battery held charge well, and it wasn’t overheating that day. I hadn’t used it much in the past two weeks.

At first I suspected deep discharge, because a cheap crappy lamp was plugged into the laptop — the kind that drains the battery completely. So I tried resetting the battery. When that didn't work, I removed the battery and tested it - it's completely drained and won't charge.

I connected the laptop to power without the battery - it doesn't respond, even though it should. This worries me the most, because it doesn't see any power source and won't turn on. I've tried different chargers, removed the main battery, removed the CMOS battery - nothing works. No lights at all. Nothing. F*cking dead.

What should I do? Any idea what could have happened?