won’t start - Charged battery all turns over but nothing

Hi new to this forum . Brought 1.2c3 off a friend for sons first car . The battery was flat was running ok before she said . Charged battery all turns over but nothing. AA came round claims it’s the immobizer and everything else ok. I noticed only certain things work when the ignition on tho. The central locking stopped key fob don’t work battery changed to boot won’t open nor will the heater switch on. Is this a immobiliser issue or think could be something else? All fuses checked bis reset still no joy help appriceated cheers

Hi. What is the year, fuel type and engine size of the car that is stated on the V5 if UK or other official document if not UK.

What radio do you have in there?

Check that the immo chip is present in the fob. It's a small black removable chip. You can see it in this link to the Early C3 transponder key fob parts (plip) fix

Car 53 plate 1.2 petrol . Sony radio but was the the standard one before and was the same . Chips in the key checked that