I spoke to Ben now. Paypal changed their setup in a way that broke the link between the payments and premie renewals, so indeed the system stopped working.
Thing is, only a literal handful of people still have a paying premium account - i.e., almost nobody outside this thread - and they only cover like 5 percent of Ben's annual hosting costs. So it doesn't really make any sense for him to fix the problem, when in any case it helps so little and in the near-ish future, he'll have to pull the plug on the site entirely.
Can we just give him money?
Not even 'please keep the site going' money, but 'thank you for keeping the site going so long' money.