Had the same here today regarding an INR.
He has emailed us twice in which we responded showing the tracking details images and that the item had arrived, then this morning the third messages says he’s really unhappy that he’s not getting a response from us so we presumed he had opted out.
We have had this before and its so frustrating for a seller not to be able to contact a buyer regarding an order, you think they would open up the messaging between buyer and seller when a purchase is made.
The only option for us was to message him via his mobile number luckily there was one there, but I suppose contacting amazons customer by phone is also out of policy so you can’t win.
Good thing is as soon as we sent the message saying we have responded to all messages twice and the tracking shows the item had been delivered and if this wasn’t the case we will pass this over to Royal Mails investigation team he responded via amazons messages saying he had found the item!
The crazy world of amazon!