A security camera don't work

I bought 3 cameras (Spotlight Cam Plus Plug-In) from you a couple of months ago. They were working fine, but a week ago one of them started not connecting to the network. I tried to find out what was wrong, I turned off the camera, restarted it, tried to connect it to the network again, nothing, it doesn't respond. What do we do, I send it back to you and you send me another one obviously? Is it under warranty right? Thank you very much--