AirPods won’t connect

I’m inheriting my moms old AirPods (it’s just the left AirPod and they are first generation). I already pressed the forget device on my moms phone and took the device off her Find My app. But the AirPods still won’t connect to my phone even when I hold the button in the back like usual. When I open the case the light will be green but when I press the back button the light will turn white for as long as I hold it then return back to normal. The AirPods and my phone are right next to each other but still won’t connect.