I plugged in the unit but nothing’s happening.

Confirm it is wired correctly.  Check the lights behind the grating. Should at least see a solid red light. If the red light is off or flickering, try another outlet or power supply. If that doesn’t solve the problem, the unit likely needs to be replaced. If the red light is solid,  check the green light next to it. If it’s off (and possibly flickers briefly at power-up), the SD card may be corrupted and needs to be replaced. If the green light is flashing steadily, that’s a good sign and the unit is trying to connect. Check the HDMI cord and that the TV is on and actually set to the right HDMI channel.