Why doesn't the Platypus survive in captivity?

When I visited a zoo near Sydney (1991), I saw at least one specimen of every animal found in the wilds of Australia, except (Ornithorhynchus anatinus), the Platypus.

When I asked our zoo guide why they had none on display, he said, “They refuse to live in captivity. When we catch one and try to display it, they die shortly afterwards, even when we give them everything they could possibly want, they still don’t survive. We don’t know why that is, but they are the only animal on Earth, that is like that.” He then showed me and some other tourists, an exhibit that had plenty of photographs of them. They are indeed, IMHO one of the most fascinating creatures on our planet, and someone once said about them, “they appear to be what would have evolved, after a nuclear war.”

Is it true that this animal cannot live in captivity, or was the guide just telling me that, as some kind of “urban legend?” The Wikipedia listing claims that some have lived to age 17, “in captivity.”

Anyone (maybe a zoologist or veterinarian?) from OZ have the skinny on this, Mate?