Can't Enter Invalid Mode

I have just replaced the Brake Booster Assembly on my 2010 Prius. Everything is back together, and I filled the Brake Fluid reservoir and connected HV and 12V batteries. Last step is to bleed the brake lines and I do not have TechStream. When I try to go into Invalid Mode, I can never get the brake symbol in lower right to Flash. I have another 2010 Prius and have no problems getting that one into Invalid Mode, tried it 3 times today and no problems. The 12V battery seems fine, around 12.5V. I have disconnected the 12V battery again and let it sit, but still cannot get in the mode. I'm wondering what else I can check?

 

Yes, I have set the parking brake. I watched the NutzAboutBolts video a few times. Also I have another 2010 Prius and went back and forth between the two vehicles. I could repeatedly put the one Prius into Invalid mode, but on the one I am trying to Brake Bleed I implement the same steps and cannot get the indicator to flash.

 

Thanks so much for the additional feedback. It seems like Techstream is perhaps the next step, and that sounds like fun to have and get working anyways We actually have 3 Prius in our family so getting familiar with Techstream may be a good thing down the road. As for the Invalid mode on this car - no I have never seen it work. I've only used it once before on the other Prius after I replaced the rear calipers. Your suggestion about not detecting the parking brake should be looked into. Perhaps that is the reason.