If your car keys aren't turning or twisting in the ignition, there could be a few reasons for this. First off, car ignitions use wafers within the barrel lock to accept your key. After some time as well as wear and tear, those wafers might be damaged and are unable to unlock the ignition. Similarly, the physical key itself may be damaged and worn out. In so doing, it won't engage with the wafers properly to unlock your car's ignition. Otherwise, modern cars also have plenty of safety features that may prevent the key from being turned. For example, the steering lock might physically lock out the ignition, as well. To fix this, all you need to do is give the steering wheel a wiggle and it should unlock it. If not, you can try jiggling the keys, spraying some grease in the ignition lock, or using the spare key.