Update.
Somehow I got lucky as I received my NEXUS approval email today. It only took 5 weeks, and no new interview required.
The letter says I need to wait to receive my new card and then activate it.
The NEXUS card number is the same as my old expired card, so I will try and use the old card at the airport as we go on our cruise in 5 1/2 weeks, as most people are reporting it takes a few months to recieve the new card.