always worth checking https://www.photo.net/ … but license may vary

Standard is for US buildings to be supplied with 240v center-tapped (single-family), 208Y120 3-phase (light commercial/multifamily), or 480Y277 3-phase (large commercial, light industrial).

120V is never supplied on its own.

Most 240V appliances work fine down to around 200V since they’ll often be used with nominal 208Y120 power after voltage drop.

Are you sure you have 240/120V split phase service and not 2 legs of 208Y120?

If so, I’d contact an electrician or the utility company - sounds like the problem is upstream

Discombobulator

reboot it?

Ths is sad