The FTP problem is solved. For reasons known only to itself, the software that runs the backend of my hosting provider decided it would cache the error message. Once I cleared cache, I reset my password and all is happy.
This brought about a rather unwelcome realization. It is not the case that there are some software companies whose secret (or not so secret) goal is to tear the fabric of reality asunder and summon the Great Old Ones. This is in fact the stated or unstated goal of all software development. And I test it for a living – complete with the unstated goal that the software does not in fact warp reality to the point that Cthuloid tentacles curl around the straining edges of the space time continuum-thingy. Aside from anything else, it takes a boatload of LOX, several tons of brimstone, and a spit that would put skyscrapers to shame to properly cook the things, and then you need to find the brave souls willing to actually eat several tons of Cthulhumari.
No, much better to keep the gate between dimensions firmly locked. Padlocked. With extra thick chain and bonus spiky bits.
Now you know why software testers have a kind of graveyard humor about them. We only hope we’ll get to enjoy one when the time comes.