If your Honda Accord is attempting to start but fails to do so after changing the ignition and keys, there could be a few potential issues at play.

1. Ignition Switch: It's possible that the new ignition switch you installed is faulty or not properly installed. It may not be communicating with the car's electrical system, preventing it from starting. Double-check the installation and connections to ensure everything is secure and correctly fitted.

2. Key Programming: Most modern vehicles, including the 2004 Honda Accord, use electronic key systems that require proper programming. If the new keys were not programmed correctly, the car's immobilizer system may be preventing it from starting. Some key fob programming can be done by the vehicle owner, while others may require a professional locksmith or dealership to assist with programming.

3. Battery Issues: If the car was left running for an extended period before the ignition was changed, it's possible that the battery has been drained. Insufficient battery power can cause the starter motor to struggle or fail to engage. Check the battery voltage with a multimeter. If it's low, try jump-starting the vehicle or charging the battery.

4. Security System: In some cases, if the ignition switch is changed or replaced, the car's security system may go into an anti-theft mode and prevent the vehicle from starting. Refer to your Honda Accord's owner's manual or contact Honda customer service to determine if there is a security system reset procedure you need to follow.

If you have checked and addressed these potential issues but the problem persists, it may be necessary to consult a professional mechanic to diagnose the problem accurately. A mechanic will have the expertise and equipment to perform more advanced diagnostics and resolve the starting issue with your Honda Accord.