My battery went flat on my tk barina so we jump started it and the head unit won't turn on neither will the radio the radio comes on when the door is closed when the door is open it won't come on... The lights are on on the head unit desplay but the radio won't switch on.......

In the link

https://www.justanswer.com/australia-car/gyqys-cylinder-head-bolts-torque-holden-barina-tk.html

Cylinder Head Bolts - Camshaft Support Housing and Cylinder Head Mounting Bolts .............. 25 N.m+60°+60°+60°+15° (18 lb ft+60°+60°+60°+10°)

https://www.google.com/search?q=2007+holden+barina+cylinder+head+torque+specs

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these had issues of not starting when cold and missfiring only when cold
this was due to valves sticking due to carbon build up
head of and get valve guides modified as per holden info (scrapper counter sunk guides)

What make of car?

try ringing a car audio shop to get the code

dose the car try to turn over

battery and dirty terminals is a good assumption
have the battery load tested

Your radio is in theft lockout, you need the security code that came with the owners paperwork new.

If battery is flat (discharged) that could be one of the problems. Charge the battery or try jump starting from another vehicle, if possible. If it still don't start after trying those two things, it's probably the starter gone bad.
If it starts after charging or jumping, have your battery load tested and
your alternators output checked. Make sure you didn't leave something on for example headlights or something plugged into accessory outlet, could be the reason battery went flat.
In a nut shell, one of these caused this. Bad battery, bad alternator, bad starter or something draiedn battery. Hope this helps.

depends on how old the battery is ,if it it is more than four years old chances are it will not come back to where it was because it went so flat .would jump it again if it starst okay on a jump ,would change battery goodluck

TEST YOUR ALTERNATOR AND HAVE THE BATTERY CHECKED IF THEY ARE OK
YOU MAY HAVE ELECTRICAL SHORT