2005 Prius, replaced coolant flow control valve, reconnected battery. Now have all warning lights on

As you mentioned disconnecting and reconnecting the 12V battery, be aware you need to cycle the start procedure twice. The first power-on cycle after reconnecting the battery will only reach IG-ON. The next time you turn the car on, it should go to READY mode.

If it doesn’t, the next step is to read the error codes (or have someone read them for you).

Each warning light corresponds to a particular system ECU. If a light is on, it means that system has set one or more diagnostic trouble codes (DTCs). To find out the specific issue, you need to read the DTC(s). Once you have them, post them here for further assistance.