AirPod gen 4 anc not connecting

Hi, I got a replacement for my airpod. I followed the steps on how to reset them - forgetting the device etc. when I’ve tried to reset them it says that the case and both AirPods are not mine. This is not true as I’ve only replaced one of the AirPods. I’ve had a look on my account and can’t see the device anywhere so not sure why the error message is showing