Why is my device but light blinking red

[Nutsofresh]

My device light is blinking red all the other lights are green

[plemans]

What extender do you have? 

The manual goes over what the led's mean. 

You can find them on the support site. 

There's a support site with access to manuals, firmware, install guides, etc.
Go to https://www.netgear.com/support/
Type in your model number and from there it'll take you to the above.
Its a great resource to start with.