I am in Zimbabwe and just had the exact same problem. I did what you said and it worked perfectly the first time. Thank you so much. My husband is six foot four and had to climb in through the boot because he didn't realize the key was in the remote! What a relief. Thanks again!Hi,
We are a Chevrolet dealer, WH Brand Ltd, and experience this all the time with Captiva's as we disconnect batteries on stock vehicles for security.
The easiest way around it is to connect the new/charged battery and then make sure all doors, bonnet, tailgate are closed. Then get both keys and press the locking button 4 times on each key (make sure you do both keys) followed by pressing the unlock button 4 times on each key. You should find all doors will be unlocked then.
It seems that after a flat or disconnected battery the keys and door locks get out od sync, but this always seems to sort it. On a very rare occasion I've had to do this twice but normally works first time.
Hope this gets you sorted.