Good home-repair question — answering as the UphillTech team:
Call the power company back. You lost a pole. Here's how your house normally works. Here's what happens when a hot wire breaks. That's simple enough, right? Half the 120V loads croak. And all the 240V loads... right? But wait. What if they are both on? Say that water heater cycles on. This. This is why the electrician and the power company read near-120V on both legs, declared victory and went home. At the time they checked it, the water heater or other 240V load happened to be cycled on. What they neglected to check was the voltage across the 2 hot legs, which should have read 240V but would...
Full answer by Harper - Reinstate Monica: https://diy.stackexchange.com/a/184022 (CC BY-SA 4.0).
Need help with this? UphillTech.