Security light is flashing after repairing engine

We need to start with checking for codes. Clearly the vehicle thinks it is trying to be stolen so it has entered a theft event.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

What repair to the engine did you do? Was the battery unhooked when you did this? If so that was the cause. Sometimes when you unhook the battery and then reconnect it the theft system thinks someone is trying to steal the vehicle. Usually unlocking the vehicle with the key fob will deactivate it. Do you have a fob? If not, try unlocking the driver door with the key and see if that turns the system off. If not, we may need a scan tool that can go in and turn this off.

Unfortunately we don't have a manual on this vehicle and don't offer a similar one here in the USA so we can't provide specifics about the system but I am sure we can figure something out. Thanks

I understand. The flashing security light is the cause of the engine not cranking or starting. When the vehicle thinks it is being stolen it deactivates the starting ability.

So if we solve the security light flashing issue, I suspect we will get the vehicle started. So all you did was change the spark plugs?