Immobiliser problems after flat battery

[sun123]

The car had a flat battery, and this was replaced with a new one.

They remote key, 1 button one, opens and unlocks the doors fine, but will not start the car.

The red and green lights on the rear view mirror flash alternately, when turning to position 2 and trying to start the car.

I have tried the following without any success:
- disconnected the battery for a few mins to see if anything resets
- replaced remote key batteries for new ones
- resynced the key using the manual's instructions

But the car still will not start.

What can I do?

Please help

Thanks

[sun123]

Also, it seems like all the warning lights are on on the dash.

This car is my aunt's car, so I don't know much about it - what is the cause of all the warning lights to be on?