The laptop not turning on and not charging

@hadidiginet if it does not turn on with a known-well charged battery, you will need to do some power rail checking on your motherboard. It could be as simple as a bad power button to as complex as multiple failed components on the motherboard.

Now, for you to check your circuity, we will need to know the exact model of your motherboard. To work on the motherboard, use this Lenovo LOQ X90 Hardware Maintenance Manual The motherboard model will be printed directly on the board. It is usually around the RAM memory slot. Let us know what that number is (It could be a LA-N221P). Then we have to hope that schematics are available. Right now, just having done a quick search, it appears as if schematics are not yet available in the public domain. That would mean you would have to use a multimeter and check common components etc. Just in case, you also want to post some really well focused pictures of your motherboard (both sides) with your question. That way we can see what you see. Adding images to an existing question

The most probable cause is a motherboard power circuit failure (often the DC jack, charging IC, or MOSFETs on the board).

If it was just RAM or HDD, the laptop would power on but not boot (fans, lights would start). Since it’s completely dead, the power delivery path on the motherboard is almost certainly faulty.