**** Can’t start Prius - lost master keys ; blah blah blah ###

Welcome to PriusChat!!

Have you checked the engine oil level lately?

Don't know about the 'Autel Maxisys ms906 Ts scanner', but the dealership would use techstream to program a new key.

You can have a similar setup by purchasing a 'mini-vci' cable ($20) and installing techstream on a windows device.

It sounds like you'll need to reseed : https://weboctopus.nl/lexus-scion-toyota-pass-code-by-seed-code-calculator.php

If that is too much, you might try calling local locksmiths, dealerships, or consider an AAA membership and tell them you lost the key.

 

I think the standard answer when you lose ALL of the working keys is:
You must buy a new ECU WITH at least one working key because the claim is that is the only way.
Cost: Something like $800.
But ask a dealer or two......and a locksmith or two.

 

That’s not correct for 2004 and later Prius models, at least in North America.

“All Keys Lost” is exactly the situation for which Toyota has provided the Smart Code Reset procedure in the Toyota Techstream diagnostic system, as a less-costly alternative to replacing the transponder key ECU (or in later generations, ID code box), which is deliberately mounted in a hard-to-access location.

Smart Code Reset is officially available only to Toyota dealers and to independent shops and locksmiths who are eligible for a Security Professional subscription to techinfo.toyota.com, but as @SFO has kindly pointed out, third parties now sell anyone the service of computing the required pass-code numbers. You also need a Toyota Techstream system that can communicate reliably with the car, of course.

If you haven’t worked with the Smart Key system before, I highly recommend reviewing Toyota’s training manual, Smart Key System: Course T973B Handbook, especially Section 7 (Smart Key System, 2004-2009 Prius), available (to anyone) by subscription to techinfo.toyota.com.

 

You need to either have it towed to a Toyota dealer and spend $$$$ to have it fixed, or find a mobile locksmith with the equipment to do it and spend $$ to $$$. Those are your options.