I have a SLV-N55 SONY VCR. The remote is RMT-V402A VCR (new and the light works). The VCR will not come on using the remote. Otherwise it works just fine. Is there a way to check out the VCR sensor?

If possible. reinstall your vcr code in your existing remote.
consider using another remote [ set to your vcrs code ] -- remotes sometimes low cost at dollar / thrift stores.

You can see if the remote is transmitting an infrared signal by using the camera on your mobile phone. Turn on the camera on your phone and point the remote at the lens and press a button on the remote , if the remote is transmitting a signal you will see a flashing light emitted from the front of the remote.
If no flashing light is visible , check the batteries and the contacts. Clean with contact spray or alcohol and a toothbrush. If the batteries fit loosely , then carefully pull the springs and/or the flat contact plates in the battery compartment slightly out with a small flat screwdriver or nail file etc. to ensure a good connection onto the battery terminals. Make sure the batteries are inserted correctly.
Try new batteries.