Help getting started with Roku devices, including setup, connecting your device to your TV, linking a Roku device to your account at my.roku.com/link, adding channels, subscribing to services, and more.
Not very helpful article, but generally the three things suggested for this(especially if not seeing red light), is to plug your unit into the wall and do a factory restart of your device. If it wasn't previously plugged into the wall, may just do a System Restart before the Factory Reset. The third is to replace the power supply cable and the power supply adapter.
Sometimes, just unplugging for a bit will solve the problem.