Airpods Pro - genuine serial number but iPhone won't verify them

Hi there. I purchased a brand-new-in-box, still sealed pair of Airpods Pro from someone local on Facebook Marketplace this evening. I confirmed the plastic seal (shrink-wrap with a pull-tab) was intact before paying for them and taking them home.

I have paired them with my iPhone 12 which is running the most up to date iOS version. However ,my iPhone says that the Airpods cannot be verified as genuine and may not behave as expected.

I used Apple Support live chat earlier this evening and got their help to validate that the serial number of the Airpods is genuine.

I have tried forgetting the connected Airpods device in Bluetooth settings, resetting my iPhone and resetting the Airpods but when I pair the Airpods again they still can't be verified.

I've seen other queries re: this issue being known about by Apple who are looking in to it - is there any update on the investigations and can anyone help me resolve this? Thank you :)