On Friday, December 20, 2019 at 1:40:25 PM UTC-5, Clare Snyder wrote:
On Fri, 20 Dec 2019 14:39:41 +0630, Oumati Asami
wrote:

The light in the laundry room stops working after worker had worked on
the ceiling in the next room.

There are two wires coming in to the light (or one in one out). Before I
flip the switch, both wires are not charged as tested by a tester. After
flipping the switch, both are charged. Yet, the light just won't light.

I removed the light and plug it in to a socket, it works.

Question:

1) did the test (both wires not charged and then charged after flipping
the switch) I do make sense?

2) how could the work in the other room affect the light next room? I do
see that there are three wires in the switch box, none of them neutral
or ground. They are all live wires. Two on one side of the switch, one
on the other side. The two are charged, the other is only charged after
the switch is flipped.
The worker damaged the neutral connection somewhere. The "juice" is
getting in, but is not getting out.

I would agree, IF he's did his testing with the light in the circuit.
But if not, the above does not explain how he says he has TWO wires
that are energized.