It looks like the reason will not be addressed soon, then. His ID photo looks very youthful. Possibly he is busy with something like school or getting a job and the hobby has been let slide. But the site works for me, so I don't really think it's a site problem, especially since it used to work and I doubt that you have had a major upgrade to your computer system that may have caused it.Because if you had, then that might have been the first thing to come to mind.
I know that my Yahoo account will often do something very weird and after a few days it settles out again, as whoever was in the Mess Things UpToday crew has whatever they did reversed and put back to normal, or at least, made to work.
"Affordable prawns" is a joke, a relic of the old afp group, so now I'm thinking that he is using an old photo and may be a lot older than that, which could imply an entirely different set of reasons why his email address has changed.
Prawns are one of the quieter running jokes in Discworld (usually having to do with someone ordering prawns delivered and they spoil, or Ridcully thinks that happened). There were a lot of in-jokes on alt.fan.pratchett, e.g., people would have status lines in their signature files that gave relationship cues based on their online conversations. One version had people who were very friendly but not actually dating being each other's "Tolerable Frog" (from the joke, "I have given up the search for a handsome prince and will settle for a tolerable frog"). Multiples of such relationships existed, so a sig line could include something like "tolerable frog to x, rapturously engaged to y, raptorally engaged to z, member of p's guardsmen" (some of these I just made up because it's been over twenty years and I forget the details).
Where were we? Oh yeah...
Gaspode the Wonder Dog => Ge Fordge's Compenydyum of Sex Majick