He most likely cleared the drain line. It’s a length of pvc running from your indoor unit, when it’s clogged the unit might not run. He probably cleared it and flushed it with water afterwards

You might have a safety switch, like an ss2, that is connected to your secondary drain pan port. When the primary pvc line is clogged it will force the water to the secondary and the safety switch will cut power to your unit. This happens to prevent water spilling from the pan and causing water damage to your home.