The AirPods are locked to a previous owner's Apple ID. This could indicate the pods were purchased then returned for a refund after the original buyer paired to their iPhone, but never cleared when returning. In other words your supposedly new AirPods are really pre-owned. If you don't know the original owner this may be impossible to clear the lock. This is more likely to happen with some of the third party resellers, and relatively unlikely when buying direct from Apple.
The best advice is to reject the AirPods and return to the seller for a full refund (or exchange to genuinely factory-new AirPods). If it was my choice I would be returning to any third party reseller, and buying replacements direct from Apple, either online or in a physical Apple Store.