Disconnect all the network cables connected to the router, unplug the power, wait30 seconds, plug the power back in. If the LEDs are solid with nothing connected to it, the router is most likely defective.
You can try resetting to factory default (all settings in the router restored back to factory default), by power up the router, wait 30 seconds for it to boot up, find the "reset" at the back panel, press and hold it for 10 seconds and then release it.