Why doesnt my lock button work

Hello, Celinelinea.

Thank you for visiting Apple Support Communities.

Here are some steps I would recommend going through when experiencing this issue. If you have a protective case installed on the device, be sure to test the Sleep/Wake button without the case installed.

Buttons and Switches

Sleep/Wake button won't lock or unlock iPhone

1. To lock the phone, press the Sleep/Wake button. Note: By default, if you don't touch the screen for a minute, iPhone locks automatically.
2. To unlock iPhone, press the Home button or the Sleep/Wake button, then slide the slider.
3. If either of the above steps don't work, try turning iPhone off and then on again.
4. If the iPhone will not power off, reset it.
5. Try to lock or unlock the phone.

If the issue still persists, see the section labeled Issue not resolved.

iPhone: Hardware troubleshooting

http://support.apple.com/kb/ts2802

Cheers,

Jason H.