He must be a lucky locksmith. I suspect the problem is that the actuator on the tip of the lock cylinder has broken off. It's the pin with two ears on it that you see in the picture. The stem is usually pot metal and after repeated use they crack and the clock starts ticking until they snap and fail. Actually a common issue with that design. Replacement is the same as replacing the complete cylinder except you need some long thin pliers to reach in and fish out the broken actuator piece that will be stuck in the ignition switch actuator cam in the bottom of the cylinder cavity.
Removal to determine if that is the problem is simple, disconnect the negative battery cable and wait a minute, now look under the steering column plastic shields and you will find the hole marked 2 in the image. Use a small rod or even a pen to reach in there and you will find a button. Turn the key to the run position and press that button in, the key and cylinder should just pull right out now. With it out look at that piece, is it there? If no then that is the issue, if it is there then it may be the cam itself that broke but that isn't very common as it is steel.
If it's broken off, fish out the broken piece. You should be able to get a replacement that will slide in. Take it to the locksmith with the old one and they should be able to use the two to make you a good part that uses your original keys.
Images (Click to enlarge)
Aug 13, 2020 at 5:41 PM