I have uninstalled, deleted databases, deleted caches, rebooted computers and devices, reinstalled, and it still does not work. Out of six different options (three web versions, legacy app, new app, and iOS) I have five different versions of the database and nothing I do appears to change any of them.
For those of you who appear to think I'm an idiot: Yes, I have submitted a support ticket. Given the holiday, I was (obviously wrongly) hopeful that someone here may have run into this issue and resolved it so that I can resolve it rather than waiting for support to respond. I have worked as a software developer for decades and done technical support in the past, so I'm not exactly fresh off the technology farm. There is clearly something very, very broken.