Unable to complete version update. [30426][19900][740]

[Byrtha]

When I load ffxiboot.exe, it confirms my password and gives me the maintenance notice, but when I attempt to click past that it gives me the error in the title (still in the launcher). At this point, it boots me back to the launcher's front page as if I'd just opened it.

Googling the error reveals posts from a year ago indicating I likely have earned myself a corrupt installation. They hint that the issue has been reported to SquareEnix multiple times and there might be a solution forthcoming in the form of an install validator/updater.

Did that ever happen?

If not, how do I reinstall?

PS. I did not install through Steam.