My laptop powers off just after a few seconds of turning on.Any ideas?

Hi, my laptop model is Lenovo IdeaPad S340 14iil 81vv. My laptop is having an issue. It happened when I was upgrading my ram. I don't exactly know what happened. But, when I turned on my laptop afterwards, it started having some power issues. When I press the power on button, it starts up normally, but then after 2-3 seconds, it suddenly powers off. At first i thought that maybe it was the new ram stick. But, I have tried almost everything like resetting the ram, removing the ram. Even removing and replugging the battery. Trying to power on without the battery. Not sure what the issue is. I even tried removing all the components and placing them one by one. Still the same issue.

Now, i did some research, I think that it could be a heating issue, that maybe the heating coil moved or something. Or my motherboard is toast. Also, i can't exactly take it to repair as it costs too much. I don't even know what the issue is.

So, my question is does anybody know what it could be?