3 error codes after head gasket job

Hi all,
Getting P0301, P0403 and P0352 after head gasket job, hybrid system failure message and it does not start at all.
Gasket job was not done professionally, but carefully, with youtube videos.
It was leaking coolant into cylinder 1, but the engine was working smoothly when cold prior to disassembly.
So I doubt there is anything wrong with rods, etc.
Replaced oil pan, there was no metal in there - all clean.
Disassembled, and re-surfaced head using sand paper on glass surface, after watching tons of youtube videos.
Cleaned injectors, intake manifold, pipes.
Cleaned EGR/EGR cooler, replaced all gaskets.
Installed new spark plugs (checked all spacing, etc) and new coils.
Reinstalled chain properly, but after cranking the engine when I was trying to tighten the harmonic balancer - chain marks went out of sync with marks on gears. (btw i ended just tightening the balancer with milwaukee M18) +I googled, chain going out of sync on makrs appeared to be expected after rotation. I sealed the valve cover and re-assembled all. connected hybrid orange plug+battery. Shows hybrid system fail, and does not even crank. No 'ready' light.
Potential problems - please see if I'm right or wrong:
a) maybe I did not re-surface head enough? there were no low points though after long...long sanding...
b) should i be closing the coolant reservour cover to pressurize it? i tried starting without the cap, to bleed it...
c) could EGR just not be on tight somewhere, leaking air?
d) could there be a timing chain tensioner not firing back into correct spot?(i did pre-tension it prior to inserting) should i just drain oil and disassemble it all again?
e)could there be a general air leak if i sealed something incorrectly between head/valve cover, top...
f) could there be some kind of fuse problem?
Thank you all...any advice would be very appreciated!

 

(forgot to say, i also changed PCV valve, but did not change water pump - it spins fine)
also correction: the message is 'CHECK HYBRID SYSTEM", I misspoke above. Thanks

 

Thank you for your response! It sat for 2 months. I had trickle charge on it so battery is good and it lit up with error lights when i tried to start But maybe it could be a hybrid battery discharged?
Also, I taped the HV connector with electrical tape prior to disconnecting pump hoses. (and i drained the coolant prior to all work anyhow).

The engine does not do anything whatsoever - silent. Does not turn or anything.
but i do hear that electrical sound as it powers something as prius usually does when you approach it with key in pocket. ((unless it is done by 12V battery and not hybrid one). Maybe it is hybrid battery that sat for 2 months with no charge?
well...i will check - thank you!

hmm...i just inserted the orange connector all the way and rotated the handle. so...it might be the hybrid battery???? oh boy...it is a revelation then...i did not know there is an extra 'push' there. will try next week and report (away for a week) THANK YOU

disconnected 12V and reconnected a few times - codes re-appear. someone above already suggested that the orange connector of hybrid battery might be the issue - so i inserted and rotated the handle. but they sayd there may need to be another push...will try that next week when i get back to it.
The engine doesn't even start..no 'ready' light, pumping gas pedal ields nothing.
but i do hear that electrical sound as it powers something as prius usually does when you approach it with key in pocket. ((unless it is done by 12V battery and not hybrid one)

I do hear that usual sound when relay does something once you approach the car with key in pocked, and then i hear that electrical sound when pressing the brake. But no 'ready' light....
So the hybrid battery could discharge in 2 months? that is weird, because i used to travel far, prius used to sit 3,4 even 6 months. - and then only 12V battery was discharging....always could start it again.
maybe it is the orange plug or something with it - will check, and will re-check all plugs again. Or maybe a fuse....

Interesting suggestions.
All was purchased from amazon, not original, but with thousands of good reviews ( i believe people...)
good idea to swap - thank you!! will try. would the engine at least try to crank though, if it was just spark plugs or coils? would it at least display 'ready'? it does not do any of that...
btw my codes are P0301, P0403 and P0352.
I did not have 304, but 352 is something about EGR too i think.

 

I'm using a cheap 17 dollar scanner one from amazon, (autel ms300). it has the option to erase, but the codes re-appear after erasing, and after disconnecting and reconnecting the 12V battery and orange plug of hybrid battery again and again.

 

i checked the orange plug. So it is constructed in a way that when you swing back the lever, it pushes and locks it kinda. I can't push it in further. So maybe your plug was different, or maybe this is not the issue then...Thank you for suggesting though!

 

Mr. F - THANK YOU - this actually did it! the push was to the right, and i mistakenly thought that it had to be pushed inside further (and wasnt able to, of course)Once I locked it properly, the car started! Thank you so much, and have a good holiday season!!!!

 

Hi all, wanted to say that the folks who suggested electrical problem, and especially the folks who suggested checking the hybrid orange plug - were right! The car started once i latched the orange plug properly (push and then push to the right).
So...the codes remain, but i assume my scanner isnt able to delete history. The car works perfectly, drives perfectly, does not feel like there are any misfires or egr problems. THANK YOU ALL