Why is the key not locking or unlocking my vehicle?

I have a 2003 Honda Accord sedan and the key will start the ignition but not lock or unlock any of the doors on the vehicle. What can I do to fix this?

Replace the battery in the key.

Are you talking about the actual key or the remote? If it's the key, try silicon spray in the locking/unlocking mechanism. Sometimes dust can build up, especially if you live someplace like West Texas.

If it's a normal key (not a remote fob) and it's old, it might have worn down in a way to not unlock your doors. Unfortunately if you get a replacement key made, the worn part will also be duplicated.

I assume you mean the remote is not working… Just change the battery

If the door locks are frozen shoot some PB Baster in the key holes several times and see if they free up.

Well, someone lost the original keys to the car and probably had the ignition switch swap replaced. Now you bought the car and have no original key for the door and hatch locks. You will need a locksmith to sort out the mismatched lock cylinders, probably needing 2 separate keys or having the ignition lock cylinder keyed back to the original key code for the doors to work properly. I guess you bought it and figured the RF fob worked and didn't check to see if the key worked in the door locks and are now stuck with it that way.