When I use the main key for the car (Opel Zafira B, 2007, manual), the electronics turn on but the engine won't start. It won't even make a noise as if it was trying to start. With the spare key, however, I can just start the car and drive away without a problem.
Any insights into this issue are appreciated. Thanks.
Edit: thanks for your thoughts. After your suggestions i did get back to the car with both keys and these are the observations:
1) The main key can turn the car on by itself, but only works once every four or five times. When the problem started it could turn the car on at the second try and at some point I thought it was completely broken, but after repeated tries yesterday it was turning on the engine.
2) The couple of times I tried to use the main key with the secondary key near the ignition, the engine turned on at first try. The secondary key still turns the engine on at first try as well
3) the key is not bent and there are no visual signs of problems. I did remove some grime from the key groove with a toothpick, so now it is cleaner. But still it does not turn the engine on reliably.
4) When the key fails to turn on the engine, the yellow warning for "Service Vehicle Soon" shows up.