Unity no longer won't allow me to import assets

For some reason Unity refuses to accept any meshes, no matter what format, even the fbx files I dropped in successfully only a day ago. I tried to do it in Finder (Apple Mac user), but even that did not work. I can do it via the “Import New Asset” menu, but sadly, the textures are stripped off.

Obviously, I need to solve this, otherwise my long and labor intensive project will have come to an untimely end.

Any work around or advise would be very welcome. Thank you very much.

Try reinstalling the unity editor
The settings may become default