You need to escalate it, it is very easy for the to cancel and reissue. They should not send by insecure means if they are not willing or able to.
2109/20 terms
"1.7. The Club shall not have any liability to any Purchaser or Ticket Holder for any non-delivery or late delivery of any Tickets, documents or other materials dispatched by the Club to the Purchaser and/or Ticket Holder resulting from the actions, omissions, malfunctions or interruptions of any postal services or incomplete or inaccurate personal details or addresses provided to the Club. Should any such items purchased not arrive in the post by seven (7) days before the relevant Match, and the Club has not notified the Purchaser or Ticket Holder that the Tickets should be collected in person, the Purchaser should contact the Club immediately."
2016/17 terms
"3.2. The Club shall not have any liability to any Purchaser or Seasoncard Holder for any non-delivery or late delivery of any Seasoncard, ticket, documents or other materials dispatched by the Club to the Purchaser and/or Seasoncard Holder resulting from the actions, omissions, malfunctions or interruptions of any postal services or incomplete or inaccurate personal details or Addresses provided to the Club. Should any such items purchased not arrive in the post before seven (7) days before the first Premier League Match or first Cup Match of the Season, the Purchaser should contact the Club immediately and such items shall be reissued at no extra charge."
Seems like the customer service is going backwards, unless yu contacted them more than 7 days before the game.