The Panda was once considered a "cryptid". The Okapi was thought to be mythological until 1901.
But mostly ~200 years ago.
The gorilla wasn't confirmed as a real animal until 1847, for example. As to whether anything that has ever actually been called a cryptid has been revealed, I don't know. Certainly it's been done in retrospect with things like the Okapi, but that's pretty unsatisfying - it's just a late entry in the 1800s catalog, really. Rediscoveries and giant versions or dwarf version of known animals are very different from what in many cases would require whole new orders of animalia.
I believe the Giant Squid was once considered a cryptid, but it is not anymore. In fact, it is well documented in many shows. I believe it was first filmed back in Mexico.
It almost always stay very very deep underwater, hence making everybody believe it was a hoax. It was very elusive for many centuries. So far, the Giant Squid is all I know. It would be good if more can be found though. Someone should invent a machine that can photograph literally all areas of a lake at once to see if there are really river monsters, e.g. the Lochness monster.