No cabin heat. Overheat icon flashing.

Is the coolant level low?
There are endless threads about a leak from the exhaust area or the catalyst co verter and a bypass of the leak. Or other ways to deal with that

 

So its pointing to a water pump or something . But you mentioned that its might have been replaced.
Lets see what other senior members suggest.

 

Dont know

 

I hate to say this, but if someone has already replaced the electronic water pump and thermostat - there's a high likelihood they also used stop-leak and other stuff to correct the problem; so they could "dump" the car onto someone else.
These cars DON'T blow white smoke or turn the oil into milkshake - if it did, you'd notice the engine issues right away. Those are pre-ECU old iron block engine diagnostics. The modern ECUs would catch these issues much sooner. In other words the CEL would be lit; before it ever got to that point.
My best advice is, buy one of those AP200 scanners and OBD2 HUD on sale and use OEM parts for repair. The OBD2 HUD will monitor engine conditions in real-time and alarm when parameters are set and exceeded. I don't believe the Prius alarms or stores overheat events - just a lonely flashing red lamp.

Good Luck...

You'll need to describe the traction battery charging issue in more detail; since we can't see, hear, touch, or smell what's going on - but one problem at a time.

 

Earlier year Gen 4’s had problems with coolant leaks in the exhaust heat recovery system, might be a factor.

 

There's either air in the system or it's clogged by stop-leak.
Change the water pump and follow proper procedures to 'burp' the cooling system. Make sure you crank the heater all the way up while your doing this.
Tech tip: place the car in ready mode; hit the front defogger button to fire the engine. It beats doing the chicken-dance - trying to get it into service mode. PS. service mode disables safeties - doing it my way, safeties are still engaged - so if you screw-up you won't blow anything up.

Good Luck....

FWIW; I'd probably run a Carfax on it to see what your getting into..... I've been noticing a disturbing trend where most dealerships don't even put down mileage or what they did to the car. Simply date and 'car serviced' - pretty much makes those reports useless. It probably helps resale values because you can't figure out patterns of failures on certain make and models.

 

At least I have an answer to one part of the post!

Toyota Service Information and Where To Find It | PriusChat