My 2023 Prius surprisingly wouldn't start today.

OP. Is the car typically driven infrequently? If yes you may be depleting the battery low enough to damage the 12V through sulfation but not low enough where it won't start the car. Do this enough times and eventually the sulfation and battery depletion will be enough where the almost dead 12v can't start the car.
I monitor the 12V batteries in both of my cars with an inexpensive BM2 Bluetooth monitor. When a battery get's low enough where it's in danger of being damaged I charge it up with a smart maintainer/charger. Not only does it charge the battery it also reverses the effect of sulfation ergo keeps the battery healthy.

 

My 20 Prime is back to not charging properly as the weather warmed. Charging the 12 v all night again. Not that it wouldn’t start the car, but it was at 70% and the voltage lower on the battery monitor, forget what don’t pay that much attention to voltage anymore unless it drops very low. Have other things in life to attend to, monitor tells me what I need to do fast.