Laptop does not start after assembly?

I disassembled my laptop to remove the dust in it, because a lot has accumulated there.

When assembling, however, the laptop starts up, the led on the start button comes on, but the screen stays off, and there's no start sound from the speaker either.

I'm sure that I have inserted the connections correctly and therefore I do not know what else could be the error.

Small components are built into the laptop that can be overloaded by the small electrical charge that your body has

Depending on the extent and care how you "disassembled" it and put it together, something might not be very good.
Hopefully you won't be statically charged… Otherwise the machine will be over the Jordan.

Otherwise there are many causes:
Flex-print broken, contacts shifted, or flat cable not fully inserted?

Sometimes it helps to just open it again, set all connections again, and of course pay attention to any connections that have been forgotten.