Apple Watch erase pending

I sold my watch, and erased it before sending it away in the mail. But then when the buyer received it, the activation lock was still on. So I did the steps required by going to icloud and find my device and “erase this watch”. But then the watch just waits in erase pending mode. And the buyer says they can’t do anything. How can the person who bought the watch connect it to the internet (to trigger the erase) if they can’t open the watch (because it’s locked!)?!