I had a Texmac 2017 installation and Texstudio via macports.
Recently I have to install lyx via macports, but lyx installed a Texlive basic 2018. Two texlive installed but no properly worked My priority was not lyx.
I installed Mactex (texlive 2018)
I moved /usr/local/texlive/2017 to the trash (Finder: Go/Goto Folder (Ir/Ir a la carpeta..))
sudo port uninstall lyx sudo port uninstall --follow-dependents texlive-bin
and texlive common, texlive-basic, and 4 TexStudio installed. and finnally
sudo port install texstudio
After that things work again. Thanks everybody, particularly @quark67