Will not start, no check Engine light, no dash lights, no multi-function display?

This sounds like the BCM when out, but to be sure let's run a CAN scan which is easy. You can get a CAN scanner (Controller Area Network) from Amazon for about $32.00.

here is a video to show you how:

https://youtu.be/u-4syLc-ifQ

and

https://www.2carpros.com/articles/can-scan-controller-area-network-easy

Here is how to change the BCM out which you can search Google or eBay for a rebuilt unit that comes preprogrammed. Check out the images (below). Please let us know what happens.

It gives error it’s not connecting to obd2 scanner.

There is an IG2 relay I would swap out which supplies power to the system that is not working. The relay is located in the fuse panel under the hood on the left side.

Here is a guide to help you test it and the location in the images below:

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

Check out the images (below). Please let us know what happens.

Relays are good. I had Prius mechanic check it and he said my remote doesn’t have the smart chip inside or I lost it when replacing the battery. But the thing is I never opened that side of the remote where smart chip sits. It’s not the original key fob of the car and it’s the only one I have. Now he’s telling me I need a new key chip and he will reprogram the key. I don’t understand how the key worked before without the chip.

Yep, good call there, can I ask if the security light is flashing when you try to crank it over? If so this is a security issue.