"Check Hybrid System" Warning Screen

Hi guys! First time poster...

So I was working on installing a custom stereo system in my new Prius C. I had the main 12V battery removed for awhile. I put everything back together and now I get an error screen when I go to start the vehicle:

CHECK HYBRID SYSTEM
STOP THE VEHICLE IN A
SAFE PLACE IMMEDIATELY

Vehicle will not go into ready mode and is undriveable but all electronics turn on and work. Some research on the limited amount of Prius C information so far has shown that disconnecting the 12V battery may cause this screen to show up. Also that some installers have bumped into the orange connector on the hybrid battery and this will also cause the error screen to show up. Here is what I have tried so far:

+Cycled ignition on and off multiple times (I believe they said it was 3 times for original Prius would clear this screen, no luck)
+Checked voltage on 12V battery: measures 12.3VDC under load (vehicle in start mode) and also not under load (vehicle off)
+Checked that orange plug on hybrid battery is properly inserted
+Checked for Check Engine Light (CEL) codes, none
+Checked in the factory owners manual (said call Toyota dealer immediately, no further details)
+Called Toyota dealer, said they don't know and to tow it in (no help)

I should also mention the entire interior has been removed. I made sure all essential plugs are back in, only thing not connected is the passenger seat and light for the trunk (shouldn't impact driveability as I drove it like this before no problem). Problem showed up after I disconnected the 12V battery.

I suspect there is a reset procedure to get it out of this lockdown mode but I can not find it listed anywhere nor does anyone I've talked to knows what it is. Either this or 2. I blew something up or 3. Something is still disconnected somewhere despite my searching.

Any help (besides telling me to take it to the dealer) would be greatly appreciated. Thanks!

 

Ok I left the battery on a trickle charger for 4 hours and now the battery measures 13.15 VDC. Warning light still shows up. I even tried just for fun disconnecting the battery for awhile to reset and reconnecting, still no luck.

I don't have any fancy stereo equipment hooked up (yet) besides just the new head unit. I'm not sure that the MFD would be an issue since I got the Prius C Two which does not come with factory navigation. Also the aftermarket head unit was installed in this car for about a month prior to this incident so I would think if it was a problem that it would have shown up then. But I'm willing to try anything at this point.

 

Update: I put the factory radio back in, still giving warning message. I will try checking fuses.

 

Here are some pictures of the high voltage interlock. I am pretty certain it is installed correctly...

 

Sorry for the late reply. Since my Prius wasn't moving I decided to strip it and sound dampen everything:



I just finished putting it back together last night and pushed the plug up as depicted in the picture above. Now engine would start but would still give the warning screen! So I cycled the ignition a few times and the screen cleared!

Its interesting since I don't recall bumping that switch and it isn't intuitive that it locks in like that unless you see a picture of someone elses. Thanks guys for the help!

PS: However a new problem showed up:



Code pops up immediately after being cleared so its not a one time deal apparently. I'm probably going to start a new thread for this one unless someone has an answer right away...

 

Where is this sensor located?