Am 02.02.2018 um 07:06 schrieb Emile Lunardon:
In my configuration the tex-gyre and tex-gyre-math packages of Miktex
are well installed.
Since I wanted to use LuaTeX, I checked, perhaps wrongly, the option
"Use non-TeX fonts (via XeteX/LuaTeX)".
The LaTeX font packages will be used for TeX fonts. For non-TeX fonts
the fonts installed on your system can be used. If you don't see the
Gyre fonts they are not installed to Windows.
To fix this, install the 4 font files:
Right-click on the font files in Windows and then choose Install (this
requires admin permissions and Windows might ask for the admin
password). Afterwards, log out from Win, log in again, then start LyX
and reconfigure it.