Hello, I had the same problem, I could not use the codes of the old boxes because www.paulmccartney.com/redeem did not work. Fortunately, the new boxes have customer service, but I had previously read that the downloadable content are managed by different sites. However, I did send an email to email@example.com, which I believe manages the vinyl section. The service was very friendly, they did not check me if I had really bought legally or if I had a box in my possession, I just explained that I had a collection and that my old boxes did not have access to downloadable content. Today I was happily able to download McCartney II again, I hope this information will help you. Sorry for the bad english.
Pal, you are awesome, I'm trying this today. I haven't been able to download BotR, AtSoS and RAM.
Thanks a lot for posting you solution!