LyX ⇒ LyX cannot find amsart.cls but lists it under tools/TeX info

[thorine]

All document classes are shown as unavailable in Document>Settings. In particular, for a working example, this is true of AMS article. An attempt to open such a document leads to a warning that amsart.cls is not installed. This is despite listing this very file (along with those for other classes) in Tools>TeX information.

I have uninstalled/reinstalled LyX to its current version. I have used Tools>Reconfigure (and had MiKTeX refresh file name database) more times than I can count.

Under paths, in LyX prefrences, I have listed C:\Program Files (x86)\MiKTeX 2.9\miktex\bin.

This all began a couple of weeks ago, as I was trying to install a custom class (for a journal's requirements). I got this to work on my laptop and home pc, but something went amiss here, and now that I have submitted that article (working on my laptop), I have time to try to undo the damage here.

Any ideas?

[scottkosty]

Not sure, but you might consider uninstalling your current version and installing LyX 2.3.4 (which was just released today). Of course, such big changes could bring even more problems your way.