AirPods (Gen 4) not pairing with mixed components

I have a Gen 4 setup made of 3 different units and can't get them to pair.

• Case: my original case from a previous set
• Right AirPod: from a newer set (left pod was destroyed)
• Left AirPod: replacement unit from Apple

When I follow the setup instructions and tap the button 3 times on amber, I get 3 low denial beeps instead of white. The pods won't pair.

My guess is the pods are still associated with their original cases. Is there any way to reset/unpair them so this case can adopt both pods? Or do I need Apple Support to wipe the serial associations on their end?