My AirPods let out a “beep beep beep” when I try to reset or restart it.

When I wanted to use my AirPods they wouldn’t connect. So, I removed the device from my Bluetooth connections and now I am unable to reconnect it back. However, when I press on the back button of my AirPods, only a green light comes out for a while then disappears. When I press for 10-15 seconds, there will only be a “beep beep beep” sound and my AirPods wouldn’t connect to my phone. How do I fix this?