LyX cannot find any TeX classes!

[Anders Host-Madsen]

I installed LyX 2.1.2 from 2.1.0. Now LyX cannot find any
classes. I kept 2.1.0, but when I run that it cannot find any
classes either. But the classes are there. It worked with 2.1.0
before I installed 2.1.2. And if I compile directly in TeXShop,
there is not problem, all the classes are there. What can I do?
Probably it's some kind of path problem.