Reconnecting AirPod Pro 2nd Gen after 'Forgetting Device' and Resetting

My AirPod Pro 2nd Gen weren't connecting properly (they are fully charged), so I 'reset' them by forgetting them on the Bluetooth settings. When attempting to set them up with my iPhone 11 Pro (software is all up to date) I receive a 'Not your AirPods' page. At this point the light on the case is green. I am then told 'press and hold the button on the back of the charging case' which I do. The light on the case then turns off, and nothing changes on the iPhone screen - I have held the button for many minutes without progress. How can I resolve this? I have attached an screenshot of the page I am stuck on. Both devices are fully charged, and all my software is up to date.