My laptop is completely unresponsive.

@tadalter Start off with the easy things. Disconnect the power from the computer by unplugging the power cord from your computer. Disconnect all external devices from the computer. Remove the battery Now hold the power button depressed for about 30sec-1min. Reapply the AC power adapter and see if your computer does show any sign of life.

Next you want to check your power supply. Make sure it has the proper voltages. Check to make sure that connectors are not bend etc. Check the DC-in jack of your laptop. Make sure there is no corrosion, debris etc. that prevents it from working. Clean it of any debris etc, use a few puffs of air to clean it out. If none of this works, get a ammeter and see if your laptop draws any amperage from the charger. After that, you need to check and see if your motherboard even gets power. For that of course, you need to open it up. Post Some good pictures of what you see. That way we can see what you see.

To work on your Lenovo use the Lenovo IdeaPad 3 15ACH6 Hardware Maintenance Manual check for proper voltage on the board side of the DC-in jack. IF it does have proper voltage going in but remans without any sign of life, then issue could be board related. Let us know if you are willing to go that deep into the weeds with that. If so, post some good, well focused pictures of your motherboard etc. with your Question. That will allow us to see what you see.

Adding images to an existing question