I just finished repairing a Lenovo Ideapad C340 where the power light would go on for 6 seconds and nothing would happen. Previously i’d repaired an Acer Swift laptop which would freeze when you tried to enter the BIOS.
In both cases the BIOS reset switch did not fix the issue. The laptop battery needed to be disconnected, in the case of the Acer Swift I also detached the coin BIOS battery, then I held down the power button and reset switch at the same time for 10 seconds.
Sort of an unintuitive solution that’s worked twice for me now though there’s plenty of other things it could have been with those symptoms.