Why Wont my Copy of a Key work?

Is it a door key or a car key?

Car keys are sometimes equipped with a microchip, meaning that a regular copy of the key will open the door but won't engage the engine.

If it's a door key, then it's possible that it's just a bad copy. Even locksmiths sometimes make faulty copies, and you can't necessarily tell by looking at it. Try making another copy from the original.

Sometimes new keys don't work as smoothly as they should.

Try pushing it in as far as possible before turning it. If that doesn't work, try pulling gently on it while you turn (just don't pull it very far out or that will guarantee it won't work).

If that fails, try wiggling the key up and down as you turn it. If that fails as well, take the key back.

If the key works at all, it should tend to start working better the more times you open the lock with it. If you have time, put the key in the lock and turn it, then remove it about 500 times; the wear should make it work easier.

Try a light filing of both sides of the key cut. May also have to file the back stop of the key cut.

It could be. Go have a key made somewhere else that knows what they're doing.

I have had this happen but sometimes it looks just perfect,the same and may be just a fraction off that that of course would make it not work.