Replaced Head Gasket. Motor starts runs 10 seconds and does a hard stop.

Did you manage to get it started and running prior to the repair?

Don't keep trying to "start" it; you'll run the hybrid battery down, compound your issues. "Starts and runs" is probably a misnomer, it's more likely just the hybrid battery trying to start it.

Double-checked all your connections? For example, the PCV valve hose going into underside of intake manifold? That one's easy to miss, will stop the engine right away.

 

The ICE is trying to start, but it is not starting. What you hear for 10 seconds is the electric motor trying to start the ICE.

What scan tool are you using. I don't think that you are reading all the trouble codes that have been triggered by the car.

 

Did you remove the disconnect on the hybrid battery? If so, did you replace it?
Make sure you push it in, hard, flip the lever completely, then push to the right, hard.
It seems to be very sensitive. I would say yes it's connected, because the battery is
turning the engine over. If it was running before, Then it will run afterward, if you
put everything back together. What about the PCV valve hose? That's a common and
easy thing to miss.... I missed it the last time I cleaned my egr system. You'll have to remove
the airfilter box to get to it.

I suspect it's something simple.
But....
[SOLVED] P261C Code: Low Coolant Pump 'b' Control - Fix Now!

P3000 – What Does It Mean and How To Fix It - OBD2PROS

Make sure that you have EVERYTHING connected. Double and triple check.
Disconnect and reconnect to make sure.

 

When you say "Hard Stop", after cranking and not firing. I'm assuming you mean that the motor stop cranking isn't normal. That sounds like a timing chain/setting issue. Hopefully you did the two full manual rotations and double check the timing marks during your assembly, to ensure your correctly timed and no valves were hitting the pistons. If you didn't and the timing is off, you just bent some valves - Start all over again....
If your off by just a tooth, some cars will run, but they'll run like crap - chances of bending valves are still there, when the VVT starts adjusting...

 

The Blue Driver scan tool is not capable of reading all the trouble codes in your Prius. Normally, when you get a P3000 code, you will also get a hybrid system trouble code that is not being detected by your scan tool. Also, after the engine does not start, there are a few additional trouble codes that get triggered, which you are not seeing.

Why do you think the hybrid battery is dead? If that were the case, the engine would not try to start.

My recommendation is to purchase a scan tool that is capable of communicating with all the systems (ECUs) in the Prius. Read this thread: https://priuschat.com/index.php?posts/3290690
The Autel AP200 is a good choice. It is on sale right now on Amazon for $55.20.